Future tense of o)/mnumi, first person singular; see also omicron 241.
Hesychius omicron816, commenting (according to Adler and Latte) on Homer, Iliad 1.233, where the headword occurs (web address 1), glosses with the thematic present tense form o)mnu/w.
Other forms of this verb appear at omicron 260, omicron 297, omicron 298.