The headword is either masculine accusative singular or neuter nominative/accusative singular of the adjective eu)kto/s; neuter accusative if it is extracted from the quotation given here, though there are plenty of earlier examples (Euripides, Xenophon, Menander, Josephus, Lucian, et al.).
[1] Read zwgrh/sontes (future participle), from Agathias, instead of the Suda's zwgrh/santes (aorist). For Narses (478-573), of Armenian descent, eunuch and general during the reign of Justinian, see generally nu 42); also under alpha 112, alpha 2394, alpha 4094, beta 490, delta 579, epsilon 917, epsilon 2328, epsilon 2631, theta 99, pi 1234, pi 2311, pi 3225, sigma 1303 and tau 753.
[2] Agathias [alpha 112], Histories 38.24-6 (= 1.22 Niebuhr), on the Battle of Ariminum (present-day Rimini, Italy; cf. alpha 3884) in 553 CE. See also alpha 202, pi 110, pi 1234, and Frendo (30-31).