can't tell (one's) arse from (one's) elbow

(redirected from can't tell their arse from their elbow)

can't tell (one's) arse from (one's) elbow

rude slang Is very stupid or dimwitted. I'm not surprised to hear that Denise got lost two blocks away from her house—she's can't tell her arse from her elbow.
See also: arse, elbow, tell
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