The headword is the present active participle, feminine nominative singular, of the verb u(posmu/xw. Identically glossed in Photius (upsilon243 Theodoriidis) and other lexica, including the Etymologicum Magnum, where it is identified as a rhetorical word; cf. Etymologicum Gudianum s.v. u(posmi/xousa.
Examples of the word in this precise form are almost entirely confined to lexicography; perhaps, therefore, generated by one of the several instances, in the corresponding accusative case, in Christian writers (e.g. three in Gregory of Nyssa, two in John of Damascus; and see also the poet George of Pisidia, On the Persian Expedition 2.193).