What does "paracentric" mean?

Paracentric: Deviating from circularity; changing the distance from a center. Paracentric curve (Math.), a curve having the property that, when its plane is placed vertically, a body descending along it, by the force of gravity, will approach to, or recede from, a fixed point or center, by equal distances in equal times; -- called also a paracentric. -- Paracentric motton or velocity, the motion or velocity of a revolving body, as a planet, by which it approaches to, or recedes from, the center, without reference to its motion in space, or to its motion as reckoned in any other direction.