play fast and loose

1. To behave dishonorably; to make a promise and fail to deliver on it: “It sounds like a good deal, but I hope that real estate agent isn't just playing fast and loose with me.”

Idioms and Phrases

Be recklessly irresponsible, unreliable, or deceitful, as in This reporter is known for playing fast and loose with the facts . This term probably originated in a 16th-century game called “fast and loose,” played at country fairs. A belt was doubled and held with the loop at table's edge, and the player had to catch the loop with a stick as the belt was unrolled—an impossible feat. The term was already used figuratively by the late 1500s, especially for trifling with someone's affections.