impair
v. C1 Advanced US //ˌɪmˈpɛɹ// UK //ɪmpˈeə// im·pair
v. to make something less effective or worse. You use this when a person or thing is not working as well as it should.
v. to reduce the effectiveness, quality, or value of something; to cause a loss of physical or mental ability.
The heavy rain began to impair the driver's vision.
The new law aims to prevent substances that might impair a pilot's judgment from being used before a flight.
While the initial damage was minor, the constant exposure to saltwater eventually began to impair the structural integrity of the ancient stone walls.
From Middle English impairen, empeiren, from Old French empeirier, from Early Medieval Latin impeiōrāre, from in- + Late Latin peiōrāre (“worsen”), from peiōrem (“worse”), comparative of malus (“bad”).