"Illegal gambling" refers to participating in betting or games of chance that are prohibited or against the law. It means engaging in activities that involve wagering money or assets in situations that are not lawful. Full definition
Although the policy game is a major source of illegal gambling profit, betting on sports is, perhaps, the largest in revenue and public interest. (si.com)
Yes, and when you bet $ 10 on a football game with your friend, you are being a bad American for participating in illegal gambling and not declaring all of your income. (religion.blogs.cnn.com)
Despite evidence to the contrary, he claimed that these games constituted illegal gambling and were not classified as a game of skill. (sportsinsights.com)