The headword is the third person singular, present indicative, of the deponent verb mna/omai. This form appears twice in Homer, at Odyssey 16.77 -- the scholia to which provide the gloss here -- and 19.529 (web addresses 1 and 2).
same entry in Photius (mu481 Theodoridis) and elsewhere.
Other forms of this verb appear in the Suda at mu 1174 and mu 1177.
cf. also epsilon 990.