'The Wanted' Singer Tom Parker -- 'Glad You Came' Is About Orgasms

One of the singers from "The Wanted" has finally settled the debate -- STRONGLY insinuating the band's hit song "Glad You Came" is really about having an orgasm ... not hanging out with some chick you like.

The video (shot recently in New York) shows "Wanted" singer Tom Parker (left) singing the song on the street with two fans.

Everything's going fine at first -- maybe a little pitchy -- but on the last verse, Tom changes the lyrics, singing instead, "I'm glad you GUSHED" ... and gestures near his crotch.

The debate's been raging for months -- so we gotta ask ...