What it means
A bad egg is someone dodgy, untrustworthy, or just plain trouble, the sort who’ll let everyone down when it matters. It’s the opposite of a good egg, and it leans on that old idea that one rotten egg can stink out the whole basket. Feels a bit old-school, but it still lands as a polite way to call someone shady.
Usage examples
"Watch out for him, he’s a proper bad egg — nicked the raffle cash and flogged his nan’s biscuit tin at the car boot."
"Steer clear of him, he has always been a bit of a bad egg."
"Most of the lads are sound, it is just one bad egg causing trouble."
Where it comes from
An egg can look perfectly sound on the outside yet be rotten and stinking within, and that is exactly the idea: a bad egg is a person who seems fine but turns out to be dishonest, worthless or no good. The phrase is gently old-fashioned and almost fond in its disapproval, the sort of thing said with a shake of the head about the one rogue in an otherwise decent bunch.
Other ways to say it
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