Yes, balk is a Scrabble word!
...and is worth 10 points in Scrabble, and 12 points in Words with Friends
balk
Verb
1. Refuse to comply
Noun
1. The area on a billiard table behind the balkline
2. Something immaterial that interferes with or delays action or progress
3. One of several parallel sloping beams that support a roof
4. An illegal pitching motion while runners are on base
What Scrabble words can I make with the letters in balk?
3 Letter Words
2 Letter Words