adj. & n.
adj. acting by rotation (rotary drill; rotary pump).
n. (pl. -ies) 1 a rotary machine. 2 US a traffic roundabout. 3 (Rotary) (in full Rotary International) a worldwide charitable society of businessmen, orig. named from members entertaining in rotation. Rotary club a local branch of Rotary. rotary-wing (of an aircraft) deriving lift from rotary aerofoils.
[ med.L rotarius (as ROTA) ]