[pis-tuh
n] 
| 1. | a disk or cylindrical part tightly fitting and moving within a cylinder, either to compress or move a fluid collected in the cylinder, as air or water, or to transform energy imparted by a fluid entering or expanding inside the cylinder, as compressed air, explosive gases, or steam, into a rectilinear motion usually transformed into rotary motion by means of a connecting rod. |
| 2. | a pumplike valve used to change the pitch in a cornet or the like. |
[pis-tuhn] | Walter, 1894–1976, U.S. composer. |
pis·ton (pĭs'tən)  (click for larger image in new window) n.
[French, from Italian pistone, pestone, large pestle, from pestare, to pound, crush, from Late Latin pistāre, frequentative of Latin pīnsere, pīnsāre.] |
piston (pĭs'tən) Pronunciation Key
(click for larger image in new window) A solid cylinder or disk that fits snugly into a hollow cylinder and moves back and forth under the pressure of a fluid (typically a hot gas formed by combustion, as in many engines), or moves or compresses a fluid, as in a pump or compressor. |