Dankness is the noun: the unpleasantly wet, cold quality of a place. You feel the dankness of a cellar; a cave has a dankness that clings to your clothes. It names the state, not the place itself. It is a fairly uncommon, slightly bookish word. Most people just say the room is dank, or talk about the damp, rather than dankness. You will meet it in writing that is trying to make you feel the air. It does not pick up the online ‘cool meme’ sense in ordinary use; it stays with the wet-and-cold meaning.

陰濕、潮冷（指那種感覺；口語多半直接說 dank）