to make or cause to become worse; diminish in ability, value, excellence, etc.; weaken or damage: to impair one's health; to impair negotiations.
verb (used without object)
to grow or become worse; lessen.
Origin of impair1
1250–1300;Middle Englishempairen, empeiren to make worse < Middle Frenchempeirer, equivalent to em-im-1 + peirer to make worse < Late Latinpējōrāre, equivalent to Latinpējōr-, stem of pējor worse + -ā- thematic vowel + -re infinitive suffix; cf. pejorative
Related formsim·pair·a·ble, adjectiveim·pair·er, nounim·pair·ment, nounnon·im·pair·ment, nounpre·im·pair·ment, nounself-im·pair·a·ble, adjectiveself-im·pair·ing, adjectiveun·im·pair·a·ble, adjective
late 14c., earlier ampayre, apeyre (c.1300), from Old French empeirier (Modern French empirer), from Vulgar Latin *impeiorare "make worse," from assimilated form of in- "into, in" (see in- (2)) + Late Latin peiorare "make worse" (see pejorative). In reference to driving under the influence of alcohol, first recorded 1951 in Canadian English. Related: Impaired; impairing.