know (one's) shit

(redirected from knows their shit)

know (one's) shit

rude slang To be very knowledgeable, especially in a particular area. That piano tuner really knows his shit—you won't believe how good the ol' Steinway sounds now. A: "I don't know about running this play, it seems like the wrong move." B: "Don't worry, Coach knows his shit."
See also: know, shit
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.