The headword, extracted from the quotation given, is the perfect active participle, masculine/neuter genitive singular form, of the verb pari/sthmi (cf. pi 570); see generally LSJ s.v.
[1] The glossing participles, of the same morphological form as the headword, are from the verbs prou+pa/rxw and e)ni/sthmi respectively.
[2] Quoted approximately from Aristophanes, Knights 398-399 (web address 1), with scholion; cf. epsilon 3095. The chorus is speaking of Kleon (kappa 1731). Here the object of the verb meqi/sthmi, I change, is in the genitive, which indicates a partitive connotation within the passage; see LSJ s.v., Smyth §1306.