When the dealer in poker adds to the community cards (flop, turn, or river) BEFORE all active players have played their hand for the current round of betting.
The term is a verb and is generally used when the above mistake causes a player who would have most likely won the hand, to lose.
I had pocket Aces against pocket sevens. Pocket sevens min-raised me. I was going to put him all in and the dealer Gabed me. Turns out the flop gave my opponent a set, he called my all in, and cracked my aces.