Yes, mar is a Scrabble word!
...and is worth 5 points in Scrabble, and 6 points in Words with Friends
mar
Verb
1. Make imperfect
2. Destroy or injure severely
Noun
1. The month following February and preceding April
2. A mark or flaw that spoils the appearance of something (especially on a person's body)
What Scrabble words can I make with the letters in mar?
3 Letter Words
2 Letter Words