† ellipˈtoidesObs. Also 8 elliptoide. [Badly f.ellipt- (cf. elliptic) + mod.L. -oides: see -oid.] An infinite ellipse. 1731Bailey, Eliptoides.1796Hutton Math.Dict., Elliptoide, an infinite or indefinite Ellipsis, defined by the indefinite equation aym+n=bxm. a-xn when m or n are greater than 1.