inhibitor - a substance that retards or stops an activitymatter, substance - that which has mass and occupies space; "an atom is the smallest indivisible unit of matter" antioxidant - substance that inhibits oxidation or inhibits reactions promoted by oxygen or peroxides anticatalyst - (chemistry) a substance that retards a chemical reaction or diminishes the activity of a catalyst moderator - any substance used to slow down neutrons in nuclear reactors activator - (biology) any agency bringing about activation; a molecule that increases the activity of an enzyme or a protein that increases the production of a gene product in DNA transcription |