One who renders himself conspicuous by affectation of dress, manners, and speech. The word was first familiarised in London in 1881, and is a revival of the old word dudes (clothes). We have several derivations, as dudder, one who sells dress-pieces; duddery, a rag-shop; duddle, to wrap up warmly (Halliwell), etc. It is not of American origin. The term is also unisex.
He is a cool dude.
Look at that dude.