1. (v. t.) To make worse; to diminish in quantity, value, excellence, or strength; to deteriorate; as, to impair vision\, character, the mind, value.

2. (v. t.) To grow worse; to deteriorate.

3. (a.) Not fit or appropriate.

4. (n.) Diminution; injury.

abate abrade abstract abuse afflict aggravate aggrieve bate befoul bewitch blemish blight condemn corrupt cripple crucify curse curtail damage decrease deduct defile deprave depreciate derogate despoil destroy deteriorate detract dilapidate diminish disadvantage disparage disserve distress do a mischief do evil do ill do wrong do wrong by doom drain eat away embitter endamage envenom erode exacerbate extract file away get into trouble harass harm hex hurt infect injure irritate jinx leach lessen make worse maltreat mar menace mistreat molest outrage persecute play havoc with play hob with poison pollute prejudice purify put back reduce refine remove retrench rub away ruin sap savage scathe shorten spoil subduct subtract taint take away take from tarnish thin thin out threaten torment torture undermine violate vitiate weaken wear away weed withdraw worsen wound wreak havoc on wrong