Main Entry: pis·ton

Pronunciation: \ˈpis-tən\

Function: noun

Etymology: French, from Italian pistone, from pistare to pound, from Old Italian, from Medieval Latin, from Latin pistus, past participle of pinsere to crush — more at pestle

Date: 1704

1 : a sliding piece moved by or moving against fluid pressure which usually consists of a short cylindrical body fitting within a cylindrical chamber or vessel along which it moves back and forth
2 : a sliding valve moving in a cylinder in a brass instrument which when depressed by a finger knob serves to lower the instrument's pitch