Longman Dictionary of Contemporary English - flaw

~ n 1 a mistake, mark, or weakness that makes something imperfect; defect1  (a slight flaw in the glass) 2 a mistake in an argument, plan, or set of ideas  (fundamental flaw (=a very important mistake or weakness))  (The lack of reliable statistics was a fundamental flaw in Walton's argument. | fatal flaw (=a very important weakness that makes something certain to fail)) 3 a fault in someone's character  (Jealousy is Othello's major flaw.)