Yes, grim is a Scrabble word!
...and is worth 7 points in Scrabble, and 9 points in Words with Friends
grim
Adjective
1. Not to be placated or appeased or moved by entreaty
2. Shockingly repellent; inspiring horror
3. Harshly ironic or sinister
4. Harshly uninviting or formidable in manner or appearance
5. Filled with melancholy and despondency
6. Causing dejection
What Scrabble words can I make with the letters in grim?
3 Letter Words
2 Letter Words