(noun) a homosexual male; a man who engages in sexual activity with other men (pronounced hump-tee-doo-dee-an).
This term is devoid of derogatory connotation and is similar to the nouns describing the natives or citizens of particular countries, e.g "He's an American, she's a Russian".
"Humpty-dudeian" may refer to residents of the mythical land of Humpty-Dude, which is thought to be where Brokeback Mountain is located, however current theories suggest that this is merely a state of mind or mild delusion, such as the optimistic belief system which gives currency to the idea that saliva is a viable alternative to personal lubricant.
From "to hump
(verb) - to have sex" and "dude
(noun) - a human being of the masculine gender"