Feminine nominative singular of this epic/poetic adjective, evidently quoted from somewhere; same or similar glossing in other lexica.
Twice in Homer, Odyssey (3.316 repeated at 15.13), it occurs in the feminine accusative singular, in the phrase thu+si/hn o(do/n "a fruitless journey" (web address 1); and a scholion there has the gloss matai/an.