Hypertext Webster Gateway: "parabola"
From Webster's Revised Unabridged Dictionary (1913) (web1913)
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.
From WordNet (r) 1.7 (wn)
parabola
n : a plane curve formed by the intersection of a right circular
cone and a plane parallel to an element of the curve
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