Definition of inhibitor?

A thing that takes up space and lives there

When we are talking about inhibitor in an enzyme, it basically means the inhibitor binds to the enzyme and stops or inhibit the enzyme from functioning. Inhibitor slows down and stops the enzyme activity, by binding to either of the two sites on the enzyme. Inhibitors bind to either the active site of the enzyme (where substrate was suppose to bind to the enzyme at, so we call this competitive inhibition), or inhibitor binds to the allosteric site of the enzyme (we call this non-competitive inhibition)