not know one's ass from one's elbow

idiom

chiefly US, informal + impolite
: to know nothing : to be stupid
Don't take his word for it—he doesn't know his ass from his elbow.

Dictionary Entries Near not know one's ass from one's elbow

not know one's arse from one's elbow

not know one's ass from one's elbow

not know one's own strength

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“Not know one's ass from one's elbow.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/not%20know%20one%27s%20ass%20from%20one%27s%20elbow. Accessed 7 Dec. 2022.

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