sharp as a razor

(as) sharp as a razor

1. Literally, having an extremely sharp point or edge. Be careful picking up those shards of broken glass! They're as sharp as razors. No one but Mommy or Daddy is allowed to use this carving knife, OK Tommy? It's sharp as a razor, and could take your whole finger off if you're not careful!
2. Very intelligent, witty, and quick-thinking. My grandmother's became very physically incapacitated as she grew older, but her mind was as sharp as a razor until the day she died. Of course Ellen is our valedictorian—she's sharp as a razor!
See also: razor, sharp
Farlex Dictionary of Idioms.

sharp as a razor

 
1. very sharp. (*Also: as ~.) The penknife is sharp as a razor. The carving knife will have to be as sharp as a razor to cut through this gristle.
2. and sharp as a tack very sharp-witted or intelligent. (*Also: as ~.) The old man's senile, but his wife is as sharp as a razor. Sue configure things out from even the slightest hint. She's as sharp as a tack.
See also: razor, sharp
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • razor
  • (as) sharp as a razor
  • razor-sharp
  • sharp
  • (as) sharp as a tack
  • sharp as a tack
  • look sharp
  • the sharp end
  • sharp as a needle
  • (as) sharp as a needle
References in classic literature
Bar's knowledge of that agglomeration of jurymen which is called humanity was as sharp as a razor; yet a razor is not a generally convenient instrument, and Physician's plain bright scalpel, though far less keen, was adaptable to far wider purposes.
Little Dorrit
A jockey's life is difficult and stormy (with apologies to Rodgers & Hammerstein), and my admiration is for the man from Killarney, with a brain as sharp as a razor and a nerve as cool as the deep waters of Lough Leane, who propelled Best Mate into history on Thursday, March 18, 2004.
Letters: Praise for man who rode Mate into history books
THORNTON GATE, sharp as a razor this season, can send soon-to- retire trainer Peter Easterby off with a final big race triumph in the Bic Razor Lanzarote Hurdle at Kempton today.
GOLDEN GATE