Gambling was the act of wagering against odds in order to profit. This often took the form of games.
In Chicago, the First Doctor gambled away the TARDIS again, this time in a game of cards with a businessman named Buchanan. He did, however, win a purple Oldsmobile 88 in another game. (PROSE: The Mother Road)
The Twelfth Doctor gambled in Vegas, winning non-stop; he told Clara that it was simple mathematics. When taken to the owner of the casino to explain how his system worked, the Doctor explained in great detail how he always chooses the most likely probability based on all the factors of rolling dice. (COMIC: Gangland)