invalid

a. [ Pref. in- not + valid: cf. F. invalide, L. invalidus infirm, weak. Cf. Invalid infirm. ] [ 1913 Webster ]

1. Of no force, weight, or cogency; not valid; weak. [ 1913 Webster ]

2. (Law) Having no force, effect, or efficacy; void; null; as, an invalid contract or agreement. [ 1913 Webster ]

n. [ F. invalide, n. & a., L. invalidus, a. See Invalid null. ] A person who is weak and infirm; one who is disabled for active service; especially, one in chronic ill health who is unable to care for himself. [ 1913 Webster ]

v. t. 1. To make or render invalid or infirm. “Invalided, bent, and almost blind.” Dickens. [ 1913 Webster ]

2. To classify or enroll as an invalid. [ 1913 Webster ]

Peace coming, he was invalided on half pay. Carlyle. [ 1913 Webster ]

a. [ See Invalid, n. ] Not well; feeble; infirm; sickly; as, he had an invalid daughter. [ 1913 Webster ]

v. t. [ imp. & p. p. Invalidated p. pr. & vb. n. Invalidating. ] [ From Invalid null. ] To render invalid; to weaken or lessen the force of; to destroy the authority of; to render of no force or effect; to overthrow; as, to invalidate an agreement or argument. [ 1913 Webster ]

adj. deprived of legal force.
Syn. -- nullified. [ WordNet 1.5 ]

adj. tending to invalidate or prove false.
Syn. -- disconfirming. [ WordNet 1.5 +PJC ]

n. The act of inavlidating, or the state of being invalidated. [ 1913 Webster ]

So many invalidations of their right. Burke. [ 1913 Webster ]

‖n. [ F. ] See Invalid, n. [ 1913 Webster ]