Conch'oid, n.

(kŏŋk'oid), n. [Fr. conchoide, from Gr. κόγχοειδής, from κόγχη, shell, and εἶδος, form.] (Geom.) A curve, of the fourth order, first made use of by Nicomedes, who invented it for the purpose of bisecting an angle. Math. Dict.