What it means
A mug is an easy mark, someone gullible who’ll believe any old chat and end up paying over the odds. Telling someone don’t be a mug is basically wise up and stop getting played. Different thing, getting mugged is being robbed in the street, not just looking daft. Nobody wants either, but the first one’s avoidable.
Usage examples
"He dropped 150 quid on a dodgy bag outside Stratford and acted gassed. Mandem told him straight, bruv, don’t be a mug."
"Don't be a mug, nobody doubles your money in a week without a catch."
"They saw him coming and sold the old banger to the poor mug for double."
Other ways to say it
Editors of this term
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