험담이 · 험담을
badmouthing, slander, speaking ill of someone
Example
다른 사람의 험담을 하는 건 좋지 않아요.
It's not good to badmouth other people.
Word parts
험 harsh+담 talk
Literally 'harsh talk' about someone.
Good to know
험담하다 is the verb; casual younger speakers often say 뒷담화하다 or 뒷담 까다 instead.