Yes, big is a Scrabble word!

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