An informal goodbye greeting. Usually used to indicate that the recipient is somehow defeated, unworthy, or left behind; hence their worthiness to appear only as a comic strip character in the funny pages.
An insult meaning one who explores the rectums of others, implying that the recipient of the insult - usually a male - engages in homosexual anal intercourse. The term is derived from 'ass', and 'Magellan', the famous Spanish explorer who attempted to sail around the world in the early 16th century.
That uptight ass magellan across the street wouldn't let me borrow his lawnmower when mine broke down.