per-

American Heritage® Dictionary of the English Language, Fourth Edition

1. Thoroughly; completely; intensely: perfervid.
2. Containing an element in its highest oxidation state: perchloric acid.
3. Containing a large or the largest possible proportion of an element: peroxide.
4. Containing the peroxy group: peracid.
5. Slang Very: percool, as in "That shirt is percool, man!”

Wiktionary

1. non-productive Denoting the sense "by" or "per", as in perchance or perhaps.
2. non-productive In verbs: denoting the sense "through", as in perforate.
3. non-productive In verbs: denoting the sense "thoroughly", as in perfect.
4. non-productive In verbs: denoting the sense "to destruction", as in pervert.
5. non-productive In adjectives and adverbs: denoting the sense "extremely", as in perfervid.
6. chemistry Forming nouns and adjectives denoting the maximum proportion of one element in a compound, as in peroxide.
7. chemistry Added to the name of an element in a polyatomic ion denote the number of that element (usually four).

GNU Webster's 1913

1. A prefix used to signify through, throughout, by, for, or as an intensive as perhaps, by hap or chance; perennial, that lasts throughout the year; perforce, through or by force; perfoliate, perforate; perspicuous, evident throughout or very evident; perplex, literally, to entangle very much.
2. (Chem.) Originally, denoting that the element to the name of which it is prefixed in the respective compounds exercised its highest valence; now, only that the element has a higher valence than in other similar compounds; thus, barium peroxide is the highest oxide of barium; while nitrogen and manganese peroxides, so-called, are not the highest oxides of those elements.