To behave recklessly, irresponsibly or deceitfully with no regards to the consequences of said actions.
Alastair said "I'm going to buy some sex dice to spice up the bedroom " and Henry replied "on the university wifi? That's fast and loose!"
by G1nger January 21, 2017
to behave recklessly, irresponsibly, or deceitfully toward someone or something, such as acting in a manner that contradicts conventions or guidelines
Wow! He sure does play fast and loose with money.
by The Return of Light Joker November 16, 2009