n. a gymnast who performs rolls and somersaults and twists etc.
n. a glass with a flat bottom but no handle or stem; originally had a round bottom
n. a movable obstruction in a lock that must be adjusted to a given position (as by a key) before the bolt can be thrown
n. 平底玻璃杯, 一杯的容量, 杂技演员, 翻斤斗者
[机] 滚光机, 滚筒, 齿轮换向器