ETYM An onomatopoetic word, expressing quick, jerky motion; Old Eng. bob bunch, bobben to strike, mock, deceive.
1. A hair style for women and children; a short haircut all around.
2. A hanging weight, especially a metal ball on a string.
3. A short abrupt inclination (as of the head).
4. A small float usually made of cork; attached to a fishing line; SYN. bobber, cork, bobfloat.

1. To cut hair in the style of a bob.
2. To move up and down repeatedly.