Tacnode

A Double Point at which two Osculating Curves are tangent. The above plot shows the tacnode of the curve $2x^4-3x^2y+y^2-2y^3+y^4=0$. The Links Curve also has a tacnode at the origin.

See also Acnode, Crunode, Double Point Spinode

References

Walker, R. J. Algebraic Curves. New York: Springer-Verlag, pp. 57-58, 1978.