{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.