invalid

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. One who is incapacitated by a chronic illness or disability.
2. adj. Incapacitated by illness or injury.
3. adj. Of, relating to, or intended for invalids.
4. v. To incapacitate physically.
5. v. Chiefly British To release or exempt from duty because of ill health: "I was not quite sick enough to be invalided out, even though I was of no more use” ( Mary Lee Settle).
6. adj. Not legally or factually valid; null: an invalid license.
7. adj. Falsely based or reasoned; faulty: an invalid argument.

Century Dictionary and Cyclopedia

1. Not valid; of no force, weight, or cogency; weak.
2. In law, having no validity or binding force; wanting efficacy; null; void: as, an invalid contract or agreement.
3. Deficient in health; infirm; weak; sick.
4. n. An infirm or sickly person; one who is affected by disease or disabled by any infirmity.
5. n. Hence Something that is damaged, or the worse for wear, but not so much as to be wholly unserviceable.
6. To affect with disease; render an invalid: chiefly in the past participle.
7. 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.
8. To cause one's self to be registered as an invalid.

Wiktionary

1. adj. Not valid; not true, correct, acceptable or appropriate.
2. n. One who is confined to home or bed because of illness, disability or injury
3. n. Any person with a disability.
4. adj. Intended for use by an invalid.
5. v. UK To exempt from duty because of injury or ill health.

GNU Webster's 1913

1. adj. Of no force, weight, or cogency; not valid; weak.
2. adj. (Law) Having no force, effect, or efficacy; void; null.
3. n. 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.
4. adj. Not well; feeble; infirm; sickly.
5. v. To make or render invalid or infirm.
6. v. To classify or enroll as an invalid.

WordNet 3.0

1. adj. no longer valid
2. adj. having no cogency or legal force
3. v. force to retire, remove from active duty, as of firemen
4. v. injure permanently
5. n. someone who is incapacitated by a chronic illness or injury