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Longman Dictionary of Contemporary English
piston ring
▪ These resemble crop-sprayers, but with piston engines - hence the avgas there.
▪ A piston engine reacts immediately to power, just like a car.
▪ All light aircraft maintenance workshops would most certainly have one for synchronizing and timing port and starboard magnetos on piston engines.
▪ After a piston engine, starting a turbine can seem strange.
▪ Pardue's aircraft had metal on the oil filter screens as well as part of a piston ring.
▪ But as the barrel swung it would push a small piston that, in return, moved the hand lever.
▪ Controlled by computer and battery-powered hydraulics, they push or pull like pistons to damp movement by the walls.
▪ He used a cane and tried to walk fast and his hips bobbed like pistons gone awry.
▪ Here, the float arm closes a horizontal piston, fitted with a washer against the valve seating.
▪ It consists of an upright cylinder containing a twelve-inch piston with rod two and a half inches in diameter.
▪ Some of their multi-cylinder motor cycle engines have pistons little bigger than thimbles.
▪ The steel piston is fitted with brass piston rings which, says Hytek, makes for longer life.
▪ This is a wonderful piece of ancient machinery of indeterminate age, and consists of a crank-driven triple piston pump.
The Collaborative International Dictionary

Piston \Pis"ton\, n. [F. piston; cf. It. pistone piston, also pestone a large pestle; all fr. L. pinsere, pistum, to pound, to stamp. See Pestle, Pistil.] (Mach.) A sliding piece which either is moved by, or moves against, fluid pressure. It usually consists of a short cylinder fitting within a cylindrical vessel along which it moves, back and forth. It is used in steam engines to receive motion from the steam, and in pumps to transmit motion to a fluid; also for other purposes.

Piston head (Steam Eng.), that part of a piston which is made fast to the piston rod.

Piston rod, a rod by which a piston is moved, or by which it communicates motion.

Piston valve (Steam Eng.), a slide valve, consisting of a piston, or connected pistons, working in a cylindrical case which is provided with ports that are traversed by the valve.

Douglas Harper's Etymology Dictionary

1704, from French piston, from Middle French piston "large pestle," from Old Italian pistone "a piston," variant of pestone "a pestle," from pestare "to pound," from Late Latin pistare, frequentative of Latin pinsere (past participle pistus) "to pound" (see pestle). As a verb from 1930.


n. 1 A solid disk or cylinder that fits inside a hollow cylinder, and moves under pressure (as in an engine) or displaces fluid (as in a pump) 2 (context music English) A valve device in some brass instruments for changing the pitch vb. (cx intransitive English) To move up and down like a piston.


A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. In a pump, the function is reversed and force is transferred from the crankshaft to the piston for the purpose of compressing or ejecting the fluid in the cylinder. In some engines, the piston also acts as a valve by covering and uncovering ports in the cylinder wall. The petrol enters inside the cylinder and the piston moves upwards and the spark plug produces spark and the petrol is set on fire and it produces an energy that pushes the piston downwards.

Piston (disambiguation)

A piston is an engineering component of engines and pumps.

Piston (s) may also refer to:

Piston (optics)

In optics, piston is the mean value of a wavefront or phase profile across the pupil of an optical system. The piston coefficient is typically expressed in wavelengths of light at a particular wavelength. Its main use is in curve-fitting wavefronts with Cartesian polynomials or Zernike polynomials.

However, similar to a real V8 engine piston moving up and down in its cylinder, optical piston values can be changed to bias the wavefront phase mean value as desired. As phase values can only vary from zero to 2π, then repeat in either direction (termed phase wrapping), changing the piston coefficient changes the zero phase value contour locations across the wavefront. This property is critical to the operation of phase-measuring interferometers, which give not only the magnitude but also the sign (convexity or concavity) of a wavefront under test. Piston is physically created in the interferometer by piezoelectric actuators that translate the Fizeau interferometer reference surface along the optical axis by precise fractions of the test wavelength, usually by one quarter of a wavelength. This changes the interferometric fringe patterns and allows direct calculation of the exact wavefront error.

Piston and tilt are not actually true optical aberrations, as they do not represent or model curvature in the wavefront. Defocus is the lowest order true optical aberration. If piston and tilt are subtracted from an otherwise perfect wavefront, a perfect, aberration-free image is formed.

Piston (music)

The piston ( Breton: pistoñ, English phonetic "pist-on") is a type of oboe invented by Breton musician, teacher, and luthier Youenn Le Bihan in 1983. The pistoñ is a contemporary development of the hautbois, classical and/or baroque oboe, influenced by the bombard or talabard, the traditional double reed instrument of Brittany. It is typically rooted in the key of D and features post-mounted simple system key-work to expand its range. The tone of the pistoñ stands in a warm and rich middle ground between the trumpet-like tone of the bombard and that of the baroque oboe. The bore is similar to that of a baroque or classical oboe.

The pistoñ uses a fairly stiff reed based on cane of an approximate diameter of 12mm, very similar in size to those of the baritone oboe (approximately 9 mm in width at the tip), English horn and baroque oboe. Unlike these other oboes, however, the pistoñ reed's brass staple resembles that of the conservatoire oboe, having a cork outer layer and a cylindrical (as opposed to conical) shape to fit into the reed well of the instrument, therefore requiring neither thread to wrap the staple nor a bocal for it to fit into.

Since its debut by Mr. Le Bihan with groups such as Gwerz and Skolvan, use of the pistoñ has slowly expanded in popularity in traditional groups associated with the " fest noz" dance culture, typically accompanied by instruments such as fiddle, guitar, traverso flute, and accordion. Some other musicians who have recorded with the pistoñ are the group Koun ( pistoñ: Josik Allot ), Tud ( instruments and music by Eric Ollu ), and Penn Gollo ( pistoñ: Jean-Claude Petit ).

Initially Mr. Le Bihan was the only maker of the instrument, and he made them on only a very limited basis. Other makers soon filled the void, however, and instruments by makers such as Hervieux & Glet, Jean-Luc Ollivier and Eric Ollu began to fill the pistoñ role as well. Mr. Ollu objects strenuously to the use of the term "pistoñ". As he states on his website (translated): "I always call the instrument by its real name; oboe or baroque oboe. I suppose I could call it an Olluphone, tromblophone or some other fantastic name. Why in Brittany and only in Brittany do people call a Baroque oboe a pistoñ? One can only wonder that information available since the fifteenth century has not yet been received! Why give the name of a brass instrument to a woodwind?" (In French, piston occurs as a shortened form of cornet à pistons, the instrument known in English as a cornet.)

While Mr. Ollu might market his instruments as baroque oboes, the pistoñ differs from the baroque or classical oboe in several ways beyond the differences in reeds and keywork mentioned above. Changes in the size and placement of the finger holes have produced changes in the fingerings used to produce the notes F and F#, allowing very rapid passages to be played in E minor without the use of forked fingerings. The pistoñ is also tuned to concert standard A440 tuning rather than a historically-based tuning scheme such as A=415 or 430. Altogether these developments highlight the pistoñ oboe as an evolving instrument intended to play a contemporary popular music, rather than recreate music and performance from the remote past.

Piston (subcellular structure)

A piston (also known as a dart, prod, or tentacle) is a complex contractile organelle found in some dinoflagellates, namely the Erythropsidinium and Greuetodinium genera of the family Warnowiaceae. This group is also well known for possessing other unusually complex subcellular structures such as the ocelloid and nematocyst. Observations of Erythropsidinium samples reveal that the length of the piston is highly variable across specimens. The piston is known to be capable of repetitive and dramatic contractile motion; although its function is unknown, roles in locomotion, prey capture, and defense have been suggested.

Usage examples of "piston".

And then the pistoliers shoot them in the head with a big gun that has a kind of a piston, goes right into the brain and comes out again, ready for the next one.

The hydraulic piston dropped, carrying the bottom bowl with it, shaking the concrete pad of the floor.

Attached at about a third of the way back was the rod which led directly down into the pump, to pull the piston there up and down.

The hinge and the piston linkage were each fastened with a nut and bolt, and appeared to have been tightened by Atlas.

While he watched, the mighty piston leaped at him, then stopped with a powerful uuuuush less than four inches from his face.

Like an airborne mote within the eerily lit bowels of that colossal imaginary mechanism, he drifted past massive walls and interconnected columns of whirling drive shafts, rattling drive chains, myriad thrusting piston rods joined by sliding blocks to connecting rods that were in turn joined by crank wrists to well-greased cranks that turned flywheels of all dimensions.

The push rod was screwed into a miniature piston head which, in turn, actuated a trio of switches.

With movements so infinitesimal that a hundred might equal the thickness of a human hair, the piston head had turned, slowly but inexorably unscrewing itself from the push rod thread.

Just as a final grain of sand will tip a scale, so, at this moment, the slightest further twisting of the piston would isolate the motor switch entirely.

Furthermore, for maximum efficiency operating speeds and temperatures whole orders of magnitude greater than the piston engine were needed.

Once the bullet had left the muzzle, the pressure in the cylinder dropped and the piston traveled backwards, forcing the remaining gas into the barrel.

Her teeth clamped lightly down on the moving piston, igniting the electricity of pain-pleasure along the rigid length.

The savage plunging ripped between her thighs like a pounding piston of pleasure.

Craning her neck, she watched as the fiery piston of pleasure drove in and out of the tight-pressed tunnel.

Again her eyes opened and her neck strained up to allow her mouth to possess the ramrodding piston of lust.