Laches -- 1. Unreasonable delay or negligence in pursuing a right or claim -- almost always an equitable one -- in a way that prejudices the party against whom relief is sought. 2. The equitable doctrine by which a court denies relief to a claimant who has unreasonably delayed or been negligent in asserting the claim, when that delay or negligence has prejudiced the party against whom relief is sought.
(This week's term is courtesy of Black's Law Dictionary.)