A curve which intersects some straight line in an infinity of points (but for which not every point lies on this curve).
References
Borwein, J. M.; Borwein, P. B.; and Bailey, D. H. ``Ramanujan, Modular Equations, and Approximations to Pi or How to
Compute One Billion Digits of Pi.'' Amer. Math. Monthly 96, 201-219, 1989.