a short, jerky motion

a bob of the head.

to move quickly down and up

to bob the head.

to indicate with such a motion

to bob a greeting.

to make a jerky motion with the head or body.

to move about with jerky, usually rising and falling motions

The ball bobbed upon the waves.

bob up, to emerge or appear, esp. unexpectedly

A familiar face bobbed up in the crowd.

verb

bow , duck , genuflect , hop , jerk , jounce , leap , nod , oscillate , quaver , quiver , ricochet , seesaw , skip , waggle , weave , wobble , ball , bounce , buff , buffet , bunch , clip , curtsy , cut , dance , dib , float , haircut , hairdo , jeer , jest , mock , pendant , refrain , shake , shilling , sled , tap , trick , weight , worm