Joke
noun, の adjective
When you have a superfluous talk you aren't being serious, you're telling a joke.
じょうだん
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
冗談でもそんなこと言わないで。
Please don't say things like that even as a joke.
彼女は冗談が上手で、いつも楽しませてくれます。
She's good at telling jokes and always entertains us.
トーフグはポッドキャストで冗談ばかり言っている。
Tofugu likes joking on their podcast.