My definition of a donkey is, say your hole cards are Ah3h 3 others see the flop, the flop comes Ad3c5c you flopped 2 pair you go all in, 2 players fold, the 3rd player (the donk) has Jc6h he calls (he should have folded) with nothing hoping for runner runner clubs, the turn & river are clubs you loose, this actually happened to me.