ˈpɪstən n. 1 a
disc or
short cylinder fitting closely
within a
tube in
which it moves up
and down
against a
liquid or
gas, used in an internal-combustion
engine to
impart motion, or in a pump to
receive motion. 2 a sliding
valve in a
trumpet etc. øpiston-ring a ring on a piston sealing
the gap between the piston and the cylinder
wall. piston-rod a
rod or
crankshaft attached to a piston to
drive a
wheel or to impart motion. [F f.
It. pistone var. of pestone
augment. of pestello PESTLE]