1. a prefix meaning "through," "thoroughly," "utterly," "very": pervert; pervade; perfect.
2. Chem. a prefix used in the names of inorganic acids and their salts that possess the maximum amount of the element specified in the base word: percarbonic (H 2 C 2 O 5 ), permanganic (HMnO 4 ), persulfuric (H 2 S 2 O 8 ), acids; potassium permanganate (KMnO 4 ); potassium persulfate (K 2 S 2 O 8 ).
[ per PER, and used as an intensive ]