1. a plane curve formed by the intersection of a right circular cone and a plane parallel to an element of the curve;

The Collaborative International Dictionary of English v.0.48:

Parabola \Pa*rab"o*la\, n.; pl. Parabolas. [NL., fr. Gr. ?; -- so called because its axis is parallel to the side of the cone. See Parable, and cf. Parabole.] (Geom.) (a) A kind of curve; one of the conic sections formed by the intersection of the surface of a cone with a plane parallel to one of its sides. It is a curve, any point of which is equally distant from a fixed point, called the focus, and a fixed straight line, called the directrix. See Focus. (b) One of a group of curves defined by the equation y = ax^n where n is a positive whole number or a positive fraction. For the cubical parabola n = 3; for the semicubical parabola n = 3/2. See under Cubical, and Semicubical. The parabolas have infinite branches, but no rectilineal asymptotes. [1913 Webster]WordNet (r) 3.0 (2006):

parabola n 1: a plane curve formed by the intersection of a right circular cone and a plane parallel to an element of the curveMoby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "parabola": arc, bow, catacaustic, catenary, caustic, circle, conchoid, crook, curl, curve, diacaustic, ellipse, festoon, hook, hyperbola, lituus, sinus, tracery