The headword, presumably extracted from somewhere (but a form occurring only in lexicography), is the perfect middle/passive participle, masculine accusative singular or neuter nominative/accusative singular, of the contract verb sunere/w, I address, speak with, address together; see generally LSJ s.v.
[In her critical apparatus Adler reports that, against alphabetical order, mss A and M (corrected) transmit the lemma as suneirme/non.]
[1] The first gloss is the same form as the headword, but from the verb sumple/kw, I entwine, plait together, entangle, engage with; cf. kappa 1416 (gloss) and see generally LSJ s.v. In the Synagoge (348) and Photius' Lexicon (sigma758 Theodoridis) the glossing participle is sunestramme/non (having been twisted up, rolled up); cf. sigma 1567 and the note there (for, inter alia, a suggested emendation of the headword).