/'pɪstən; `pɪstn/
n
1 round plate or short cylinder,usu made of metal or wood, that fits closely inside another cylinder or tube and moves up and down or backwards and forwards inside it; used eg in steam or internal combustion engines to cause other parts to move by means of a connecting rod (`piston-rod) 活塞. =>illus 见插图.
2 sliding valve in a trumpet or other brass wind instrument （铜管乐器上的）活门.

n[C]
[Date: 1700-1800; Language: French;Origin:Italian pistone 'large stick for crushing', from pistare 'to crush']
a part of an engine consisting of a short solid piece of metal inside a tube, which moves up and down to make the other parts of the engine move