- an infirm or sickly person.
- a person who is too sick or weak to take care of their own needs: My father was an invalid the last ten years of his life.
- a member of the armed forces disabled for active service.
- unable to care for oneself due to infirmity or disability:his invalid sister.
- of or for invalids: invalid diets.
- (of things) in poor or weakened condition: the invalid state of his rocking chair.
- to affect with disease; make an invalid: He was invalided for life.
- to remove from or classify as not able to perform active service, as an invalid.
- to remove or evacuate (military personnel) from an active theater of operations because of injury or illness.
- to become an invalid.
- not valid; not founded in truth, fact, or logic, and hence weak and indefensible; unsound; untenable:The entire argument depends on an invalid assumption.
- deficient in effectiveness; inadequate:Self-perception is an invalid method of judging one's own biases.
- void or without legal force, as a contract:Without the grandfather clause, thousands of such warranties would now be invalid. The coupon is invalid in our state.
- not accepted or permitted because a required element or the necessary form is lacking; not usable:Anything with fewer than five characters is an invalid password, and you’ll get an error message prompting you to pick something more secure.
- a person suffering from disablement or chronic ill health
- (as modifier)
- suffering from or disabled by injury, sickness, etc
- to cause to become an invalid; disable
- to require (a member of the armed forces) to retire from active service through wounds or illness
- not valid; having no cogency or legal force
- (of an argument) having a conclusion that does not follow from the premises: it may be false when the premises are all true; not valid
