Yes, mibs is a Scrabble word!
...and is worth 8 points in Scrabble, and 10 points in Words with Friends
mibs
Noun
1. A unit of information equal to 1024 kibibytes or 2^20 (1,048,576) bytes
What Scrabble words can I make with the letters in mibs?
3 Letter Words
2 Letter Words