Flecnode

on a planar curve

A point at which a node (or double point; cf. also Node) and an inflection (cf. also Point of inflection) coincide.

Thus, one of the tangents at the node has intersection multiplicity at least with the curve at that point.

References

[a1]	J.W. Bruce, "Lines, surfaces and duality" Math. Proc. Cambridge Philos. Soc. , 112 (1992) pp. 53–61
[a2]	M. Tsuboko, "On the line complex determinant of flecnode tangents of a ruled surface and its flecnodal surfaces" Memoirs Ryojun Coll. Engin. , 11 (1938) pp. 233–238