The headword (which must be quoted from somewhere) seems to be the third person singular, aorist indicative, of mu/ssomai/mu/ttomai (cognate with Latin mungo). Twice already in Hesychius: at epsilon2523 glossed with e)/pien "drank", and at epsilon2530 glossed with a)hdi/sqh "was disgusted".
The Suda's gloss (also in ps.-Zonaras and, according to Adler, the Ambrosian Lexicon) is aorist of ce/w (xi 53).