The headword is a feminine noun in the accusative singular; cf. Hesychius, and see generally LSJ s.v. peripoi/hsis. (For the cognate verb see pi 1269, pi 1271.) It also enjoys a grammatical sense, by possession, i.e. the possessive form, examples of which are at alpha 139 (gloss), alpha 1371 (gloss), and pi 405 (gloss).
The headword is taken to be quoted from the New Testament: see e.g. 1 Peter 2.9 (alluding to Exodus 19.6, 23.22), 1 Thessalonians 5.9, 2 Thessalonians 2.14, Hebrews 10.39.
[1] The gloss is the same form as the headword, but from the verb kth=sis; cf. epsilon 56, zeta 128, pi 129, and generally LSJ s.v. The headword is identically glossed in the Synagoge, Lexica Segueriana 339.31, and Photius, Lexicon pi741 Theodoridis.