knob

Concise Oxford English Dictionary © 2008 Oxford University Press:
knob/nɒb/

▶noun

• 1 a rounded lump or ball, especially at the end or on the surface of something.

  ■ a ball-shaped handle on a door or drawer.

  ■ a round button on a machine.

• 2 a small lump of something: a knob of butter.

• 3 chiefly N. Amer. a prominent round hill.

• 4 vulgar slang a man's penis.

▶verb (knobs, knobbing, knobbed) Brit. vulgar slang (of a man) have sex with.

– phrases
with (brass) knobs on Brit. informal and something more, used especially for returning an insult.

– derivatives
knobbed adjective,
knobby adjective ,
knob-like adjective.

– origin ME: from Mid. Low Ger. knobbe ‘knot, knob, bud’.