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.
(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.