I thought I would expound a bit on Snuffy's post by citing Merriam Webster:
1. General: a dry, thin, crispy bread product that may be leavened or unleavened. ("I think I'll stop by Piggly Wiggly on the way home and buy a box of crackers.")
2. Southeastern U.S.: a poor, white person from the rural American South. ("I saw more crackers at the Georgia-Florida game than at the Daytona 500 this year.")
3. Savannah, GA: anyone who is not Catholic. ("I can't believe Tommy is marrying that cracker girl from Country Day").