invalid

from The Century Dictionary.

• Not valid; of no force, weight, or cogency; weak.
• In law, having no validity or binding force; wanting efficacy; null; void: as, an invalid contract or agreement.
• To affect with disease; render an invalid: chiefly in the past participle.
• To register as an invalid; enroll on the list of invalids in the military or naval service; give leave of absence from duty on account of ill health.
• To cause one's self to be registered as an invalid.
• Deficient in health; infirm; weak; sick.
• noun An infirm or sickly person; one who is affected by disease or disabled by any infirmity.
• noun Hence Something that is damaged, or the worse for wear, but not so much as to be wholly unserviceable.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb To make or render invalid or infirm.
• transitive verb To classify or enroll as an invalid.
• adjective Of no force, weight, or cogency; not valid; weak.
• adjective (Law) Having no force, effect, or efficacy; void; null.
• noun 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.
• adjective Not well; feeble; infirm; sickly.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective Not valid; not true, correct, acceptable or appropriate.
• noun One who is confined to home or bed because of illness, disability or injury
• noun Any person with a disability.
• adjective Intended for use by an invalid.
• verb UK To exempt from duty because of injury or ill health.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective no longer valid
• adjective having no cogency or legal force
• verb force to retire, remove from active duty, as of firemen
• verb injure permanently
• noun someone who is incapacitated by a chronic illness or injury