English

Alternative forms

• know one's ass from one's elbow
• know one's head from a hole in the ground
• know the difference between one's ass and a hole in the ground

Verb

know one's ass from a hole in the ground

1. (idiomatic, vulgar) To have an adequate level of knowledge or skill; to understand what one is doing or talking about.
   • 2004, David Drake, The Reaches, ISBN 9780743471770, (Google preview):

     "Why are you so sure and they aren't?" the landsman said. . . .

     "Because Mr. Ricimer knows his ass from a hole in the ground, sir."

   • 2005 June 12, Gary M. Pomerantz, "First Chapter: Wilt, 1962," New York Times (retrieved 26 July 2014):

     Foxx gave a comic's pause. "Just goes to show you, don't it? Some folks don't know their ass from a hole in the ground."

   • 2006 Dec. 5, David Kiley, "Chrysler "Whoops" Ads Part of Important New Genre," Bloomberg (retrieved 23 Sep 2016):

     In the unofficial ad, the facilitator says about the man whose wife will be replaced, “This guy wouldn’t know his ass from a hole in the ground.”

Usage notes

• Almost always used in negative constructions to describe someone's ignorance or stupidity, such as: He doesn't know his ass from a hole in the ground.

Synonyms

• know what one is about
• know **** from Shinola