[1] : The Collaborative International Dictionary of English v.0.48

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.
   1913 webster

   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.
      1913 webster
see also:
pestle pistil piston head piston rod piston valve 

Piston >> P Words
Piston, definition of term: Piston
piston_pag1.html

Valve >> V Words
Valve, definition of term: Valve
valve_pag1.html

Relief Valve >> R Words
Relief Valve, definition of term: Relief Valve
relief+valve_pag1.html

Safety Valve >> S Words
Safety Valve, definition of term: Safety Valve
safety+valve_pag1.html

Tricuspid Valve >> T Words
Tricuspid Valve, definition of term: Tricuspid Valve
tricuspid+valve_pag1.html

Ball Valve >> B Words
Ball Valve, definition of term: Ball Valve
ball+valve_pag1.html

Bicuspid Valve >> B Words
Bicuspid Valve, definition of term: Bicuspid Valve
bicuspid+valve_pag1.html

Globe Valve >> G Words
Globe Valve, definition of term: Globe Valve
globe+valve_pag1.html

Mitral Valve >> M Words
Mitral Valve, definition of term: Mitral Valve
mitral+valve_pag1.html

Mitral Valve Pr >> M Words
Mitral Valve Pr, definition of term: Mitral Valve Pr
mitral+valve+pr_pag1.html