From Longman Dictionary of Contemporary Englishlaugh/shout/scream etc your head offlaugh/shout/scream etc your head off informal to laugh, shout etc very loudly Fans were screaming their heads off. → head
Examples from the Corpus
laugh/shout/scream etc your head off• If Hancock himself had been around, he would have doubtless squirmed as the audience laughed their heads off.• Joey stood in the door laughing his head off and Noreen peered over his shoulder, her hands over her mouth.• Louise: Ursula would have laughed her head off.• Tony races past, laughing his head off.• Then he tips her down and she's screaming her head off.• By this time Irene was emitting a steady gurgle of contentment, when she wasn't laughing her head off.• You were screaming your head off.• Old Warleigh would laugh his head off if I put reasons like that to him. 