noun

• (typically uncountable) Culpability; the responsibility for a blameworthy event.
  "No, don't blame yourself. It's my fault that we lost the game."
• A defect, imperfection, or weakness; more severe than a flaw.
  "Despite all her faults, she’s a good person at heart."
• A defect, imperfection, or weakness; more severe than a flaw.
  "As patches set upon a little breach / Discredit more in hiding of the fault."
• A mistake or error.
  "It is a fault if the ball served drop in the net, or beyond the Service-Line, or if it drop out of Court, or in the wrong Court. A fault may not be taken. After a fault, the Server shall serve again from the same Court from which he served that fault."

verb

• (transitive) To criticize, blame or find fault with something or someone.
  "For that, says he, I ne'er will fault thee / But for humbleness exalt thee."
• (intransitive, geology) To fracture.
• (intransitive) To commit a mistake or error.
• (intransitive, computing) To undergo a page fault.