a public building for gambling and entertainment
"After winning big at the slot machines, we decided to leave the crowded casino before it closed for the night."
A public building or room for gambling.
"After winning big at the slot machines, he rushed to tell his friends about their night out at the new casino downtown."
In plain English: A casino is a building where people gamble by betting money on games of chance.
"They won their vacation by playing blackjack at the local casino."
Usage: A casino refers specifically to an establishment where people gamble on games like slots and poker. Do not use it to describe a small home game or any other type of recreational venue.
The word comes from the Italian casino, which is a small or playful version of casa meaning "house." It originally referred to a summer villa or country retreat before taking on its modern sense.