In its zoological application, specifically (according to LSJ s.v.) the long-tailed cicada. Photius, Lexicon kappa605 Theodoridis has the gloss missing here: "[a creature] like a cicada which emits a single sound"; and see also Hesychius kappa2342.
Note also upper-case Kerkope, a courtesan mentioned in Philaeterus fr. 9 Kock (in Athenaeus, Deipnosophists 13.587E-F = 13.52 Kaibel): "isn't Kerkope already three thousand years old, and Diopeithes' daughter, the repulsive Telesis, another ten thousand?". The Lexica Segueriana gloss thus: "name of a courtesan, so called because of her malignity. For kerkôpes are evil-doing men". (On the Kerkopes see kappa 1405, kappa 1406. The association is also made by the Etymologicum Magnum s.v. *ke/rkwpes, who suggest Kerkope might be their mother.)