paracentric \par`a*cen"tric\ (p[a^]r`[.a]*s[e^]n"tr[i^]k),
paracentrical \par`a*cen"tric*al\
   (p[a^]r`[.a]*s[e^]n"tr[i^]*kal), 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]