Definitions of cracker:

• noun:   a party favor consisting of a paper roll (usually containing candy or a small favor) that pops when pulled at both ends
• noun:   a thin crisp wafer made or flour and water with or without leavening and shortening; unsweetened or semisweet
• noun:   a programmer who `cracks' (gains unauthorized access to) computers, typically to do malicious things

  Example: "Crackers are often mistakenly called hackers"

• noun:   firework consisting of a small explosive charge and fuse in a heavy paper casing
• noun:   a poor white person in the southern United States