osculant

adj

1. (not-comparable)Kissing; hence, touching or meeting; clinging.
2. (not-comparable)Adhering closely; applied to certain creeping animals, such as caterpillars.
3. (not-comparable)Intermediate between two genera, groups, families, etc., and having some of the characteristics of each; interosculant.

   “The genera by which two families approximate are called osculant genera.”

4. (not-comparable)Intermediate between multiple potentially reconstructible protoforms, but having a mismatch in semantics or morphology that cannot be explained through regular patterns of change.
5. (not-comparable)Tangent, touching at a single point.

noun

1. The point at which two tangent curves touch.
2. The condition that the solution to a set of simultaneous quantics, is also the solution of the corresponding set of tangential quantics.
3. a form of tacinvariant of hypersurfaces that have a point in common