That's hilariousphraseThat's extremely funny.“You named your cat Chairman Meow? That's hilarious.”That's so funnyphraseThat's very amusing.“You got your dog to wear sunglasses? That's so funny.”I'm dyingphraseI'm laughing very hard; informal and figurative.“That face you made! I'm dying.”That cracked me upphraseThat made me laugh a lot.“The last line of your story cracked me up.”That's killing mephraseThat's making me laugh a lot in this context; informal.“That impression is killing me.”