From Longman Dictionary of Contemporary Englishcrack up phrasal verb informal1 crack (somebody) upCONTROL to laugh a lot at something, or to make someone laugh a lot Everyone in the class just cracked up. She’s so funny. She cracks me up.2 CONTROLto become unable to think or behave sensibly because you have too many problems or too much work I was beginning to think I was cracking up! → crack→ See Verb table
Examples from the Corpus
crack up• Some people can't cope with the death of a loved one, and simply crack up.• I think Paul's cracking up under the strain of work.crack (somebody) up• It used to crack me up.• The cloud is like a magnet so the water goes through the cracks and goes up.• It nearly cracked me up and he could see what it did to me.• Maintenance men could tell whether a pole - wooden or concrete - is dangerously cracked before shinning up it.• It was funny, he cracked me up last night.• All those crack shits shooting up the streets?• Most of the humor consists of watching Shore crack himself up with his own Valley garble.crack-upˈcrack-up noun [countable] 1 MIa nervous breakdown2 American EnglishTTC an accident involving one or more vehicles → crack up at crack1Examples from the Corpus
crack-up• Rudi felt that many of his students had no idea they were heading for a crack-up.• For some of those years I had thought it might hold off the crack-up.• The crack-up of personal confidence, the sheer bloody hell of facing every simple decision as a major crisis.• They talked about their careers, their crack-ups, their prongs, their shrinks, their dreams. 