A shape rather like an egg or an ellipse.
A sporting arena etc. of this shape.
In a projective plane, a set of points, no three collinear, such that there is a unique tangent line at each point. (A tangent line is defined as a line meeting the point set at only one point, also known as a 1-secant.)
Having the shape of an oval.
Of or pertaining to an ovum.
A foci of the ellipse) is constant; equivalently, the conic section that is the intersection of a cone with a plane that does not intersect the base of the cone.
To remove from a phrase a word which is grammatically needed, but which is clearly understood without having to be stated.