Through; by means of.A prefix of Latin origin, meaning primarily ‘through.’ See the etymology.As an inseparable prefix of intensity, ‘thoroughly,’ ‘very,’ as in peracute, perfervid, pellucid; specifically, in chem., noting the maximum or an unusual amount, as peroxid, the highest oxid, or an oxid containing more oxygen than the protoxid, etc.n. In petrography, in the quantitative system of classification of igneous rocks (see rock), a prefix used to form adjectives, and showing that the factor or component indicated is present in any division of igneous rocks, alone or in extreme amount — that is, that its ratio to another factor is greater than : as, peralkalic, perfelic, perfemane, perfemic, etc.n. An abbreviation of period.