guffaw at (someone or something)
To laugh heartily at someone or something. ("Guffaw" is likely of imitative origin.) I grinned as the audience guffawed at the joke I'd told. I'm sorry, I didn't mean to guffaw at you, but you just look so ridiculous in that hat!
guffaw at someone or something
to laugh at someone or something very hard and raucously. The audience guffawed at the clown's antics. The old man guffawed at the clown.