(colloquial, idiomatic) A formal dinner or event thrown by politicians to raise funds.

(chemistry) any oxide of rubidium, but especially the yellow solid Rb₂O; it is a strong base, reacting strongly with water to form the hydroxide and with acids to form normal salts

(slang) An act of roughly rubbing one's knuckles across the top of another person's head with the intent of causing pain and humiliation, often while pinning the other person's head with one's free arm.

(idiomatic) A valuable feature (of software etc) overlooked by the user.

A type of toy constructed of light wood, a plastic propeller and a rubber band, propelled by repeatedly winding the propeller backwards and then releasing it into the air.

plural of rubber band airplane

The original form of contract bridge; so called because bonuses are awarded for scoring sufficient points to win games and thereby a rubber, which is the best of three games.

(sports) A position in Australian rules football: one of three followers, formerly a secondary ruckman, now an athletic player generally taller than a rover.

simple past tense and past participle of ruffle

Having ruffles. / Puffed up like a bird's feathers. / (informal) Bothered.