crack up

• IPA^(key): /ˈkɹæk ˈʌp/

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

a person cracking up (sense 1)

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.

   • 2022 October 21, Jason Bailey, “How George Clooney and Julia Roberts Quietly Became the Tracy-Hepburn of Our Time”, in The New York Times‎:

     The joy of “Ticket to Paradise” comes not from its predictable plotting or razor-thin screenplay; it’s from watching them together, from observing how the sparks still fly, and (when the former flames get drunk and let their guards down, or during the end-credit outtakes) watching them crack each other up.

3. (idiomatic, intransitive, dated in US) To become insane; to suffer a mental breakdown.

   She got through the war, but cracked up when her sister died.

   • 1936 February, F. Scott Fitzgerald, “The Crack-Up”, in Esquire‎:

     All rather inhuman and undernourished, isn’t it? Well, that, children, is the true sign of cracking up.

4. (transitive, informal, usually passive, usually negative) To cry up; to extol.

   This new computer system is not what it was cracked up to be.

   • 1939 June, George Orwell [pseudonym; Eric Arthur Blair], chapter IX, in Coming Up for Air, London: Martin Secker & Warburg, published 1948 (April 1959 printing), →OCLC, part II, page 132:

     No use, with a bloke like this, cracking up your own merits. Stick to the truth.

5. (US) To crash an aircraft or automobile.
   • 1930 December, Lawrence M. Guyer, “Chuck Luck: The Story of a Flying Dog”, in Boys' Life:

     From all directions they came to the rescue, one predominant fear gripping their hearts: Fire! Someone had cracked-up. It was for this they sped. The flames that so frequently burst from a crashed airplane became an instantaneous cauldron; many a pilot has lived through the crash to die in the fire that followed.

   • 1983, John Thorn, David Reuther, The Armchair Aviator, page 101:

     When I reported this to Burwell by telephone, he called me a Chinese ace — in those days Chinese aces were pilots who cracked up their own airplanes […]

• all it's cracked up to be

crack up (comparative more crack up, superlative most crack up)

1. (New Zealand, colloquial) Funny; hilarious[1]

   That joke was crack up.

   • 2017 April 23, “McDonald's say 'neigh' to horses through the drive-thru”, in Stuff‎:

     "It was crack up!"

   • 2020 April 20, “The curious case of a fictional spa in Westport”, in Newsroom‎:

     In town people would stop and say to me, “Hey Becky, that cat story was crack up.”

   • 2020 June 5, “Police looking into footage of woman twerking on Auckland Harbour Bridge”, in Newshub‎:

     One person said it was "crack up", while the woman who uploaded it said "I'm a do it again (sic)".

• “crack up”, in OneLook Dictionary Search.
• “crack”, in The Century Dictionary […], New York, N.Y.: The Century Co., 1911, →OCLC.