Having the best flush possible in poker. Often misunderstood as an ace high flush. In some games of poker, like omaha or hold'em, there will be the possibility of a straight flush and an ace high flush would be beat. When this happens, an ace high flush (unless it is the royal flush) is NOT the best hand, thus, it IS NOT the nut flush.
Flop:
K J of diamonds, 2 of Spades
Turn:
9 of diamonds
River:
2 of Clubs
Your hole cards: 10 Q of diamonds
Your opponents hole cards: A 7 of diamonds
opponent: "I've got the nut flush!"
You: "No, idiot, you have the seconds nut flush; I have the nut flush; I have a straight flush 9 through King, you just simply have an Ace high flush. I win, YouJustGotPwnd."
(transitive verb) To obscenely expose one's testicle or scrotum to another, either by pulling up one's shorts or by other means. A nut-flash is typically meant to frustrate or surprise the victim.
(noun) The action of nut-flashing.
Spencer: (To Lauren, aggravated) Laurrennn! Cooper nut-flashed me!