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.
Wiktionary
n. a rod or bar in an engine that connects a piston to a crosshead
WordNet
n. connecting rod that moves or is moved by a piston
Wikipedia
In a piston engine, a piston rod joins a piston to the crosshead and thus to the connecting rod that drives the crankshaft or (for steam locomotives) the driving wheels.
Internal combustion engines, and in particular all current automobile engines, do not generally have piston rods. Instead they use trunk pistons, where the piston and crosshead are combined and so do not need a rod between them. The term piston rod has been used as a synonym for 'connecting rod' in the context of these engines.
Engines with crossheads have piston rods. These include most steam locomotives and some large marine diesel engines.
Usage examples of "piston rod".
Usually, with an outside cylinder, the piston rod fits into a crosshead, and the main rod connects the crosshead to the main crank pin, near the rim of one driving wheel.
Before long, the thin trail of steam from around the fill clamps betrays the increasing pressure within the kettle, but neither the piston rod nor the wheeldriver attached to it move.
It showed a single upright cylinder, with a piston rod coming out of its top.
One of the paddles came nearly out of the water, and Adrian winced as the piston rod on that side danced wildly up and down for a moment, then again at the crunch as the paddle bit solid water once again.
Each rocking beam was moved by a single steam cylinder, mounted with the piston rod upward.
The hammer on the end of the piston rod came down on the egg….
He looked up at the piston rod as it pumped the walking beam up and down.
The engine's piston rod was connected to a long shaft that drove the forward pivot on the walking beam, converting the up-and-down thrust to the aft shaft that powered the crank that turned the Lexington's big twenty-three-foot-diameter paddle wheels with their nine-foot sweeps.