know one's arse from one's elbow

English

Verb

know one's arse from one's elbow (third-person singular simple present knows one's arse from one's elbow, present participle knowing one's arse from one's elbow, simple past knew one's arse from one's elbow, past participle known one's arse from one's elbow)

1. (Commonwealth) Alternative form of know one's ass from one's elbow