An inhibitory effect is an effect that suppresses or restrains an impulse, a desire or a behavioral process either consciously or unconsciously. In science, the term is used to mean the prevention or decrease the rate of a chemical reaction or to decrease, limit or block a bodily action or function such as that of an enzyme or organ.
An example of an inhibitory effect could be a post-hypnotic suggestion that might get a person to eat less, or to change an attitude about something or someone, etc. In science an inhibitory effect could be the use of a pharmaceutical product to block a body function, i.e. insulin to block blood sugar or antivenin to counteract snakebite, etc.