A solid cylinder or disk that fits snugly into a larger cylinder and moves under fluid pressure,as in a reciprocating engine,or displaces or compresses fluids,as in pumps and compressors.是什么意思_A solid cylinder or disk that fits snugly into a larger cylinder and moves under fluid pressure,as in a reciprocating engine,or displaces or compresses fluids,as in pumps and compressors.在线翻译_英语_读音_用法_例句