The unglossed headword is nominative singular feminine of the adjective pte/rinos. This form is otherwise attested only in Simplicius, Commentary on Aristotle's Physics 9.263 (= Eudemus fr. 50 Wehrli -- on Aristotle, Physics 192b). There is a possibility that the word might serve as a noun referring to a fern or fern-like plant. See ps.-Galen, De remediis parabilibus 14.441; cf. Dioscorides 4.184, as well as n. 2 below.
For another form of the adjective see pi 3008.
[1] This phrase involving the headword adjective, in the accusative, occurs in Greek Anthology 6.306.3 (Ariston), where the item mentioned is among the things dedicated to Hermes by a manumitted cook-slave; cf. Gow and Page, vol. I (42-43); vol. II (110-111); and further excerpts from this epigram at alpha 1146, alpha 4064, beta 34, theta 539, mu 11, tau 73, tau 74, tau 799, chi 620, and omega 294.
[2] Polybius 3.71.3-4, with some minor divergences. Here the headword does not occur, but the similar-looking word for 'ferns' does (pte/reis). This suggests that the compiler thought that the headword had, or might have, something to do with ferns.