CONCHOID

conchoid. Conchoid, n. a curve approaching a line without touching it.

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Con″choid (?), n. [[Gr. �; � shell + � form: cf. F. conchoïde.]] (Geom.) A curve, of the fourth degree, first made use of by the Greek geometer, Nicomedes, who invented it for the purpose of trisecting an angle and duplicating the cube.