|Origin:||Perhaps from bob 'to hit, punch' (13-19 centuries), from the sound.|
bob1 past tense and past participle bobbed, present participle bobbing
to move up and down when floating on the surface of water:
move on water[intransitive]TTW
The boat bobbed gently up and down on the water.
to move quickly in a particular direction:
move somewhere[intransitive always + adverb/preposition]
Mrs Foster bobbed about, gathering up her things.
to move your head down quickly as a way of showing respect, greeting someone, or agreeing with them:
He spoke to the girl, who bobbed her head.
to cut someone's, especially a woman's, hair in a bob:
her neatly bobbed hair