unilateral mistake

noun | mis·take

1. : an unintentional error especially in legal procedure or form that does not indicate bad faith and that commonly warrants excuse or relief by the court the court's power to revise a judgment because of fraud, mistake, or irregularity a clerical mistake

   a : a state of mind that is not in accordance with the facts existing at the time a contract is made and that may be a ground for the rescission or reformation of the contract

   b : a misconception at the time of an offense alleged by a defendant

   — mistake of fact
   : a mistake regarding a fact or facts especially that significantly affects the performance of a contract : a criminal defense that attempts to eliminate culpability on the ground that the defendant operated from an unintentional misunderstanding of fact rather than from a criminal purpose

   — mistake of law
   : a mistake involving the misunderstanding or incorrect application of law in regard to an act, contract, transaction, determination, or state of affairs; also : a criminal defense alleging such a mistake Note: In both contract and criminal law a mistake of law is a weaker ground for relief or acquittal than a mistake of fact.

   — mutual mistake
   : a mistake common to both parties to a contract who were in agreement about the purpose or terms of the contract reformed the contract because of a mutual mistake

   — unilateral mistake
   : a mistake on the part of one party to a contract that is usually not a ground for rescission or reformation unless one party stands to profit or benefit improperly from the mistake