common as muck
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as common as muck
Low-class. Primarily heard in UK, Australia. Considering she's wearing an outfit like that in public, she must be as common as muck.
common as muckBRITISH, OFFENSIVE
If you say that someone is as common as muck, you mean that they are lower-class and not sophisticated. Leary guessed correctly that his guests were as common as muck and planned the menu accordingly.