*acentric*

{ } a. [ Pref. para- + centric, -ical: cf. F. paracentrique. ] Deviating from circularity; changing the distance from a center. [ 1913 Webster ]

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 motion or
Paracentric velocity, the motion or velocity of a revolving body, such 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. [ 1913 Webster ]