The headword is a two-ending adjective in the masculine/feminine accusative singular or neuter nominative/accusative singular; see generally LSJ s.v. peri/pteros, on for its range of related meanings, architectural and other; and cf. already pi 1264. In the present instance it is reckoned to be masculine accusative singular, extracted (as claimed by Adler and now Theodoridis on the second half of Photius, Lexicon pi746) from Amos 3.15 LXX, para/cw to\n oi)=kon to\n peri/pteron). If that is so, however, the neuter glossing participle -- see next note -- is a puzzle. (Perhaps, instead, Ptolemy Philopator's sumpo/sion polutele\s peri/pteron in Callixenus FGrH 627 F1 = Athenaeus, Deipnosophists 5.205E (5.39 Kaibel)?)
[1] The glossing participle is the present active, neuter (nominative and) accusative singular, of the verb e)ce/xw, I stand out; see generally LSJ s.v. The headword is identically glossed in the Synagoge, Lexica Segueriana 340.3, and (as noted above) in Photius, Lexicon pi746; cf. Etymologicum Magnum 229.38 (Kallierges).