Yes, big is a Scrabble word!
...and is worth 6 points in Scrabble, and 8 points in Words with Friends
big
Adverb
1. Extremely well
2. In a boastful manner
3. On a grand scale
4. In a major way
Adjective
1. Above average in size or number or quantity or magnitude or extent
2. Significant
3. Very intense
4. Loud and firm
5. Conspicuous in position or importance
6. Prodigious
7. Exhibiting self-importance
8. Feeling self-importance
9. (of animals) fully developed
10. Marked by intense physical force
11. Generous and understanding and tolerant
12. Given or giving freely
13. In an advanced stage of pregnancy
What Scrabble words can I make with the letters in big?
3 Letter Words
2 Letter Words