Dirty /Dur-tee/ -adjective unclean vile; mean; sordid; contemptible: to play a dirty trick on someone. obscene; pornographic; lewd: a dirty joke. undesirable or unpleasant; thankless very unfortunate or regrettable hostile, insulting, contemptuous, or resentful. -verb (used with object), verb (used without object) to make or become dirty. -adverb Informal. in a mean, unscrupulous, or underhand way: to play dirty. Informal. in a lewd manner: to talk dirty. -Idioms do (someone) dirty, Slang. to treat unfairly or reprehensibly, as by cheating or slandering. -Related forms dirt·i·ly, adverb dirt·i·ness, noun