Definitions of bob:

• noun:   a short abrupt inclination (as of the head)

  Example: "He gave me a short bob of acknowledgement"

• noun:   a small float usually made of cork; attached to a fishing line
• noun:   a hanging weight, especially a metal ball on a string
• noun:   a hair style for women and children; a short haircut all around
• noun:   a short or shortened tail of certain animals
• noun:   a long racing sled (for 2 or more people) with a steering mechanism
• noun:   a former monetary unit in Great Britain
• verb:   cut hair in the style of a bob

  Example: "Bernice bobs her hair these days!"

• verb:   move up and down repeatedly

  Example: "Her rucksack bobbed gently on her back"

• verb:   make a curtsy; usually done only by girls and women; as a sign of respect
• verb:   ride a bobsled

  Example: "The boys bobbed down the hill screaming with pleasure"

• verb:   remove or shorten the tail of an animal
• name:  A male given name (common: 1 in 1818 males; popularity rank in the U.S.: #266)
• name:  A surname (rare: 1 in 100000 families; popularity rank in the U.S.: #16626)