The headword -- perhaps extracted from the Aristophanic quotation given, where it is used figuratively -- is a neuter noun in the nominative/vocative/accusative singular; see generally LSJ s.v.
[1] The headword is identically glossed in Photius' Lexicon (pi1148 Theodoridis); cf. Hesychius pi3233 and the Synagoge s.v.; Lexica Segueriana 347.24; Timaeus, Platonic Lexicon pi1001a14; and Etymologicum Magnum 686.33-5 (Kallierges). Cf. sigma 1031.
[2] Aristophanes, Birds 321 (web address 1): Tereus (turned into a hoopoe) alerts the avian chorus to the arrival of the humans, Peisetaerus and Euelpides; see Dunbar, p. 260. In this passage the Suda transmits the second person singular, present indicative active h(/keis, of h(/kw (I am come; see LSJ s.v.), whereas Aristophanes' received text -- appropriate to the context -- gives the third person dual h(/keton (the pair come).
[3] Following the scholia to the aforementioned passage.
[4] Polybius 18.18.6 (web address 2), contrasting the Greek and Roman techniques for selecting wooden stakes, transporting them, and interweaving them into barricades around their military encampments (Walbank, pp. 572-3).
[5] chi 96.