Slang of the Week: whale (noun)
a gambler who plays for extremely large amounts of money

Example: 
Stan thought he was quite the whale with his thousand dollar bets, but he had to leave the table when the big boys showed up.

Celebrity quote:
“[Kerry Packer] was a legendary character. He dwarfed the other guys (noted whales the Sultan of Brunei and Adnan Khashoggi, the arms dealer). Kerry played higher, and he played for 40 years.”
-Bobby Baldwin, president and CEO of Mirage Resorts, quoted in the Las Vegas Review-Journal

Packer was the richest man in Australia until his death in December of last year. On his gambling trips to Las Vegas, he would sometimes give his dealer a toke (tip) of a million dollars.

Like their counterparts in nature, gambling whales could be classified an endangered species, with fewer than 300 in the world. To be a genuine whale, a gambler must be wealthy enough not to sweat when he (or she) loses hundreds of thousands, or even millions of dollars in a single evening.

The natural habitat of the whale is the carpet joint—an elegant casino. The opposite, a sawdust joint, is so named because in olden days, there was actually sawdust on the wood floors in low class establishments