cracking up

Verb

crack up (third-person singular simple present cracks up, present participle cracking up, simple past and past participle cracked up)

1. (idiomatic, intransitive) To laugh heartily.
   • It was hilarious. We were cracking up the whole time.
2. (idiomatic, transitive) To cause to laugh heartily.
   • The joke about the nuns in the bath cracked me up.
3. (intransitive, slang) To tease (someone) or tell jokes at the expense of (someone).
   • He's always cracking up at me about that.
4. (dated, idiomatic, intransitive) To become insane; to suffer a mental breakdown.
   • She got through the war, but cracked up when her sister died.
5. (idiomatic) To break down or fall apart; to stop functioning; to shatter.
   • The university was really cracking up, losing faculty, students and donors, and it seemed like to go under.
6. (idiomatic, transitive) To separate a group.
   • I have to crack up that little clique.

See all 14 meanings of crack up