Yes, not is a Scrabble word!
...and is worth 3 points in Scrabble, and 4 points in Words with Friends
not
Adverb
1. Negation of a word or group of words
What Scrabble words can I make with the letters in not?
3 Letter Words
2 Letter Words
Adverb
1. Negation of a word or group of words
3 Letter Words
2 Letter Words