A whale is a player with an enormous bankroll, a term used in online and land-based casinos alike. There is already a word for players who like high stakes, high roller, but whales go well beyond high-roller betting levels. Someone who bets $50 or $100 a hand might count as a high roller; a whale can bet hundreds or even thousands of dollars on every hand, simply because they can afford to lose.
The word is sometimes used negatively. It still means a player with a huge bankroll, but it can also suggest someone who is not very good at the game. If you use it, make your meaning clear so the other person doesn’t take offence.
Whales from the operator’s side
A handful of whales can swing a casino’s monthly results in either direction. Operators manage that exposure with tailored table limits, dedicated VIP management and close monitoring, including affordability and source-of-funds checks where the regulator requires them.