What is "reciprocating engine"

Reciprocate \Re*cip"ro*cate\ (r[-e]*s[i^]p"r[-o]*k[=a]t), v. i. [imp. & p. p. Reciprocated (r[-e]*s[i^]p"r[-o]*k[=a]`t[e^]d); p. pr. & vb. n. Reciprocating.] [L. reciprocatus, p. p. of reciprocare. See Reciprocal.] To move forward and backward alternately; to recur in vicissitude; to act interchangeably; to alternate.

One brawny smith the puffing bellows plies, And draws and blows reciprocating air.
--Dryden.

Reciprocating engine, a steam, air, or gas engine, etc., in which the piston moves back and forth; -- in distinction from a rotary engine, in which the piston travels continuously in one direction in a circular path.

Reciprocating motion (Mech.), motion alternately backward and forward, or up and down, as of a piston rod.

n. piston engine

n. an internal-combustion engine in which the crankshaft is turned by pistons moving up and down in cylinders

A reciprocating engine, also often known as a piston engine, is a heat engine (usually, although there are also pneumatic and hydraulic reciprocating engines) that uses one or more reciprocating pistons to convert pressure into a rotating motion. This article describes the common features of all types. The main types are: the internal combustion engine, used extensively in motor vehicles; the steam engine, the mainstay of the Industrial Revolution; and the niche application Stirling engine. Internal Combustion engines are further classified in two ways: either a spark-ignition (SI) engine, where the spark plug initiates the combustion; or a compression-ignition (CI) engine, where the air within the cylinder is compressed, thus heating it, so that the heated air ignites fuel that is injected then or earlier.