Definitions of bum:

• noun:   a disreputable vagrant

  Example: "He tried to help the really down-and-out bums"

• noun:   person who does no work

  Example: "A lazy bum"

• noun:   the fleshy part of the human body that you sit on
• noun:   a person who is deemed to be despicable or contemptible

  Example: "Throw the bum out"

• verb:   be lazy or idle

  Example: "Her son is just bumming around all day"

• verb:   ask for and get free; be a parasite
• adjective:   of very poor quality