Final answer:
Anticholinergic drugs block receptors for acetylcholine, diminishing parasympathetic activities in the body.
Step-by-step explanation:
Drugs that block a receptor for acetylcholine are known as anticholinergic drugs. These drugs inhibit the action of acetylcholine at muscarinic receptors, thereby suppressing parasympathetic activity within organs. In contrast, cholinergic drugs would enhance the cholinergic effects, adrenergic drugs interact with the sympathetic system, and parasympathomimetic drugs would mimic the effects of acetylcholine, promoting parasympathetic responses.