laches

noun | \ ˈla-chəz, ˈlā-, -shəz \ | la·ches

1. : undue delay in asserting a right or privilege — compare statute of limitations

2. a : a doctrine permitting dismissal of a suit because a plaintiff's unreasonable delay in asserting a right or privilege has been detrimental to the defendant's ability to make a defense (as by resulting in the unavailability of witnesses or evidence) a suit barred by laches

   b : an affirmative defense based on this doctrine