(idiomatic, intransitive) To laugh heartily. / (idiomatic, transitive) To cause to laugh heartily. / (intransitive, idiomatic) To become insane; to suffer a mental breakdown.

(New Zealand, colloquial) Funny; hilarious

Alternative spelling of crackup

simple past tense and past participle of crack up

present participle of crack up

Third-person singular simple present indicative form of crack up

(idiomatic) As good as claims or reputation would suggest.