Wiktionary
yuk it up
alt. (context US English) To clown around: to behave clownishly; to joke idle. vb. (context US English) To clown around: to behave clownishly; to joke idle.
Usage examples of "yuk it up".
He has heard rumors that some Eastern Europeans can do it, but he hasn't met any of them, and they don't have much to yuk it up about at the moment.