Yes, bum is a Scrabble word!
...and is worth 7 points in Scrabble, and 10 points in Words with Friends
bum
Verb
1. Ask for and get free; be a parasite
2. Be lazy or idle
Adjective
1. Of very poor quality; flimsy
Noun
1. A person who is deemed to be despicable or contemptible
2. A disreputable vagrant
3. Person who does no work
4. The fleshy part of the human body that you sit on
What Scrabble words can I make with the letters in bum?
2 Letter Words