lach·es 
(lăchĭz)
(lăchĭz)n.
A legal doctrine that bars a claimant from receiving relief where the claimant's delay in pursuing the claim has operated to the prejudice of the opposing party.
[Middle English, slackness, negligence, from Anglo-Norman lachesse, laches, from Old French laschesse, from lasche, loose, remiss; see LUSH1.]