Yes, jab is a Scrabble word!
...and is worth 12 points in Scrabble, and 15 points in Words with Friends
jab
Verb
1. Poke or thrust abruptly
2. Strike or punch with quick and short blows
3. Stab or pierce
Noun
1. A sharp hand gesture (resembling a blow)
2. A quick short straight punch
3. The act of touching someone suddenly with your finger or elbow
What Scrabble words can I make with the letters in jab?
2 Letter Words