Yes, reb is a Scrabble word!
...and is worth 5 points in Scrabble, and 6 points in Words with Friends
reb
Noun
1. `Johnny' was applied as a nickname for Confederate soldiers by the Federal soldiers in the American Civil War; `greyback' derived from their grey Confederate uniforms
What Scrabble words can I make with the letters in reb?
2 Letter Words