Piston(n.) 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.
Thesaurus Entries
PCV valve, alternator, ammeter, atom smasher, atomic accelerator, atomic cannon, bearings, bonnet, boot, brake, bucket seat, bumper, camshaft, carburetor, chassis, choke, clutch, connecting rod, convertible top, cowl, crank, crankcase, crankshaft, cutout, cylinder, cylinder head, dash, dashboard, differential, distributor, exhaust, exhaust pipe, fan, fender, flywheel, gear, gearbox, gearshift, generator, headlight, headrest, hood, horn, ignition, intake, manifold, muffler, parking light, particle accelerator, piston, power brakes, power steering, radiator, rear-view mirror, seat belt, shock absorber, spark plug, speedometer, springs, starter, steering wheel, top, transmission, universal, valve, windscreen, windshield