BOB

noun

1. A bobbing motion; a quick up and down movement.
2. A curtsy.
3. A bobber (buoyant fishing device).

verb

1. To move gently and vertically, in either a single motion or repeatedly up and down, at or near the surface of a body of water, or similar medium.
2. To move (something) as though it were bobbing in water.
3. To curtsy.