Nouns

(n)tumblera gymnast who performs rolls and somersaults and twists etc.
(n)tumblera glass with a flat bottom but no handle or stem; originally had a round bottom
(n)tumblera movable obstruction in a lock that must be adjusted to a given position (as by a key) before the bolt can be thrown
(n)roller, tumbler, tumbler pigeonpigeon that executes backward somersaults in flight or on the ground