A shark is a skilled and more experienced poker player who often prays on “fish” and
“pigeons,” i.e. inexperienced or beginner players.
Sharks pay great attention to detail. They will feed on any and every mistake a fish makes and make them pay for it.
To use the shark play poker term in a sentence, you could hear someone say: “I lost my entire bankroll last night, didn’t realize I was at a table full of sharks until it was too late.”