The headword is aorist middle participle, masculine nominative singular, of the verb meqe/pw. Entry from the scholia to Homer, Iliad 13.567, where the headword occurs -- but in the form metaspo/menos (cf. LSJ s.v. meqe/pw: web address 1). For the Suda's omega form see also e.g. Photius mu333 Theodoridis, with the editor's note there.