This is the 5849th most frequent Japanese word.
ふざけん
The word “ふざけん” is incomplete and may be a truncation. If expanded to "ふざけんな" (fuzakenna), it means "Don't mess around" or "Don't fool around," often used in a strong or angry tone.
The term 'ふざけんな' is used as a strong expression to admonish someone for behaving frivolously or joking inappropriately.
ふざけんな、そんな冗談は許さない。
Don't joke like that, I won't tolerate such humor.
Here, 'ふざけんぼう' stems from 'ふざける' and indicates someone's playful or mischievous nature.
彼はいつもふざけんぼうで、真面目な話ができない。
He is always playful and can never have a serious conversation.
In this sentence, 'ふざけん' reflects the act of playful or ridiculous behavior, admonishing the speaker.