noun

• 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 that cracks a thing (e.g. whip cracker; nutcracker).
• The final section of certain whips, which is made of a short, thin piece of unravelled rope and produces a cracking sound.
• 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.
• (obsolete) A noisy boaster; a swaggering fellow.
• (US, derogatory, ethnic slur, offensive) An impoverished white person from the southeastern United States, originally associated with Georgia and parts of Florida; (by extension) any white person.
• (Florida, slang, derogatory) A police officer.
• A northern pintail, species of dabbling duck.
• (obsolete) A pair of fluted rolls for grinding caoutchouc.