Cracker
1) (brit. slang) crazy or insane

2) a small kind of firework filled with powder, which explodes with a sharp noise or with a series of sharp cracks.

3) one who breaks open, into, or through, as a safe, a secret code, or a barrier.

4) a thin, crisp biscuit.

5) one who throws out or utters with smartness.
(example) I dont eat crackers in church.
