Re‐gres″sion (r?‐gr?sh″?n), n. [L. regressio: cf. F. régression.] The act of passing back or returning; retrogression; retrogradation. Sir T. Browne.
Edge of regression (of a surface) (Geom.), the line along which a surface turns back upon itself; — called also a cuspidal edge. — Regression point(Geom.), a cusp.