D defs.my
Entry 1 sense Webster, 1913

Regression

/(r?*gr?sh"?n)/ · Re·gres·sion · IPA /ɹiːˈɡɹɛʃ.ən/
01 n. The act of passing back or returning; retrogression; retrogradation.
  1. 1.
    The act of passing back or returning; retrogression; retrogradation.
Phrases & compounds
Edge of regression — the line along which a surface turns back upon itself; -- called also a cuspidal edge.
Regression point — a cusp.