[cy.cloid] n [F cycloide, fr. Gk kykloeides circular, fr. kyklos] (1661): a curve that is generated by a point on the circumference of a circle as it rolls along a straight line -- cy.cloi.dal adj
[2]cycloid adj (1847) 1: smooth with concentric lines of growth "~ scales"; also: having or consisting of cycloid scales
2: relating to or being a personality characterized by alternating high and low moods--compare cyclothymic