noun Chemistry.
- any substance capable of reducing the speed of a given reaction.
adjective
- retarding or tending to retard (usually used in combination): fire-retardant construction materials.
noun
- a substance that reduces the rate of a chemical reaction
adjective
- having a slowing effect
1640s, from retard (v.) + -ant or from Latin retardantem (nominative retardans), present participle of retardare. From 1952 as a noun, “retardant substance.”