L.U.P.O.S. Share definition Flag (loo-pus) n - Abbreviated form for Lazy, Useless, Piece of Shit. Ernest is such a L.U.P.O.S., all he does is sleep all day. L.U.P.O.S. by The Nuthouse Gang October 10, 2006 0 0 Get merch Get the L.U.P.O.S. mug. Buy Now — $32.95 See more merch