be laughing (one's) head off

be laughing (one's) head off

To be laughing uproariously or hysterically. Your jokes are perfect for your speech tonight. They'll be laughing their heads off! I'm telling you, Mark's boyfriend is hilarious! I was laughing my head off when I met him.
See also: head, laugh, off
Farlex Dictionary of Idioms.

be laughing your head off

INFORMAL
COMMON If you are laughing your head off, you are laughing a lot. They were probably laughing their heads off. Note: You can use other verbs with similar meanings to laugh in this way. Laura was sitting inside, giggling her head off.
See also: head, laugh, off
Collins COBUILD Idioms Dictionary, 3rd ed.
See also:
  • be laughing your head off
  • laughing in the aisles
  • laugh (one's) head off
  • laugh head off
  • rolling on the floor laughing
  • have (someone) laughing in the aisles
  • aisle