knob

1. A rounded protuberance, especially one arising from a flat surface; a fleshy lump or caruncle.
2. A rounded control switch that can be turned on its axis, designed to be operated by the fingers.
3. A ball-shaped part of a handle, lever, etc., designed to be grabbed by the hand.
4. A rounded ornament on the hilt of an edged weapon; a pommel.
5. A prominent, rounded bump along a mountain ridge.
6. A prominent rounded hill.
7. (chiefly in the plural) A woman's breast.
8. The penis.
9. The head of the penis; the glans.
10. (by analogy with above) A contemptible person.
11. A dollop, an amount just larger than a spoonful (usually referring to butter).
12. A chunky branch-like piece, especially of a ginger rhizome.
13. A bulb of the garlic plant consisting of multiple cloves.

verb

(of a man) To have sex with.