dirty language is the same as vulgar language. Words considered rude, or swearing is dirty, or foul language

dirty languange refers those words like fu@#!$% and shi$%#@! cowboy...

Dirty language is considered a bad language. Plus, use foul language in normal conversation is extremely rude.

Just the same as in Chinese, offensive, X rated language.However I am quite sure that you know the answer already.