The loss of a winning poker hand on the very last card dealt; it is frequently followed by shock, tears, and a severe need to blow things/people up. (Halo, anyone?)
3:36pm All in preflop...equal hands...I hit a better hand on flop and turn and get rivered by my arch nemesis. Anybody with the name of Sandy that you happen to know, go ahead and punch him/her in the face for me. thx...
In "open" variations of poker such as Hold 'Em or Stud, to have one's strong hand beaten by an opponent whose stronger hand is only completed with the last face-up card, called "the river" or "Fifth Street;" or, to beat an opponent's strong hand with the last face-up card.
I had a runner runner straight flush draw against The Kid's full house but I rivered him. Sometimes you do the wrong thing for the right reason.