What it means
A bad egg is someone you don't trust an inch. They're dodgy, unreliable, or just the kind of person who brings grief wherever they go. It's an old-school way to call someone shady without going full nuclear, and it often carries that vibe of looking alright at first, then turning out rotten once they're cracked open.
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."
"Don’t lend Kyle your bike, he’s a bad egg and you’ll never see the thing again."
"Her brother’s a bit of a bad egg, always stirring it up and then acting shocked when it kicks off."
Where it comes from
This one goes back to the 18th century in English. It comes from the plain image of a rotten egg that seems fine till you crack it and get the nasty surprise. By the 1800s, bad egg was being used for a person who looked respectable enough but turned out dishonest, worthless, or suspect.
Other ways to say it
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