a colorless, liquid acid, HClO, that is a strong oxidizing agent: its concentrated solutions can form explosive mixtures with reducing agents: used in analytical chemistry, in making solid propellants, etc.
Origin:
per- + chloric
See perchloric acid in American Heritage Dictionary 4
noun
A clear colorless liquid, HClO4, explosively unstable under some conditions, that is a powerful oxidant used as a catalyst and in explosives.