The headword, evidently extracted from somewhere, is the perfect imperative middle/passive, third person singular, of the verb pari/hmi. Compare pi 593 (for gloss as well as headword), and see generally LSJ s.v.
The earliest attested instances of the headword are in Polybius (2.56.9, 2.59.3), but in the sense there of 'let [something] be disregarded'.
Perfect imperatives generally do occur in third person singular, passive voice constructions, and in formal contexts such as civic, legal, or mathematical discourse; the connotation is of something to be done with finality and decisiveness (Goodwin, 105-6).