A dry, thin, crispy baked bread (usually salty or savoury, but sometimes sweet, as in the case of graham crackers and animal crackers).

A short piece of twisted string tied to the end of a whip that creates the distinctive sound when the whip is thrown or cracked.

A firecracker.

A person or thing that cracks or produces a cracking sound, such as a whip cracker or nutcracker.

A Christmas cracker.

Refinery equipment used to pyrolyse organic feedstocks. If catalyst is used to aid pyrolysis it is informally called a cat-cracker

(slang, chiefly Britain, Australia, New Zealand) A fine, great thing or person (crackerjack).

An ambitious or hard-working person (i.e. someone who arises at the 'crack' of dawn).

(computing) One who cracks (i.e. overcomes) computer software or security restrictions.

(US, derogatory, ethnic slur, offensive) An impoverished white person from the southeastern United States, originally associated with Georgia and parts of Florida; any white person.

(Florida, slang, derogatory) A police officer.

A northern pintail, species of dabbling duck.