firecracker UK /ˈfaɪəˌkɹækə/US /ˈfaɪəɹˌkɹækəɹ/noun 3forms 1phrases 1 noun3 •A small explosive device, typically containing a small amount of gunpowder in a tightly-wound roll of paper, primarily designed to produce a large bang.She said she was awakened abruptly Friday night by the kid next door setting off a firecracker. — 2011 •(slang) Someone or something that is exciting, energetic, or unpredictable. •(slang) A peanut butter cracker baked with marijuana, similar in concept to an Alice B. Toklas brownie. formsfirecrackers Phrases with firecracker wet firecrackerA person, event, or object lacking liveliness or failing to generate excitement, especially when there was a prior expectation of liveliness or excitement.