The headword, presumably quoted from somewhere, is a feminine noun in the nominative (and vocative) plural; see generally LSJ s.v. o)/rguia (the length of outstretched arms or about six feet), and already omicron 521, omicron 522. The oxytone (Smyth, 157) headword may be generated by an earlier form, where the accent falls on the antepenult, which is instanced at, for example, Homer, Iliad 23.327 (web address 1).
[1] The headword is similarly glossed by ps.-Herodian, Partitiones 102.5, and Hesychius omicron1122; cf. Etymologicum Magnum 629.47-9 (Kallierges) and Orion [Author, Myth], Etymologicum 116.16-8.
[2] A cognate of the lemma, this is an adjective in the masculine singular; LSJ s.v. Adler also cites as identical Lexicon Ambrosianum 428.