pis·ton /ˈpɪstən/
 活塞,瓣


 Pis·ton n.  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.

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 Piston
      n 1: United States neoclassical composer (1894-1976) [syn: {Walter
           Piston]
      2: mechanical device that has a plunging or thrusting motion
         [syn: plunger]