know one's shit

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know one's shit

1. (idiomatic, mildly vulgar) To be well-informed concerning a particular subject; to have a capable command of a particular area of expertise.
   • 2005, Mike Tucker, Among Warriors in Iraq, →ISBN:

     "He really knows his shit. He knows more about guerrilla war than I could ever learn in ten lifetimes," Morales said.

   • 2011, Lev Grossman, The Magician King, →ISBN, p. 134 (Google preview):

     “Any magician can ask another magician of equal or lower level to demonstrate the test corresponding to their level or any of the levels below that,” she recited. “To prove they know their shit.”

   • 2014, Dalton Fury, Full Assault Mode: A Delta Force Novel, →ISBN, (Google preview):

     She knew her shit. . . . Without as much as a single stutter or misstep, she spoke about decisive point, synergistic execution, momentum shift, kinetic solution, and competent authority.