Merriam-Webster's Collegiate® Dictionary, 11th Edition
REGRESS
I. noun see: grade
Date: 14th century
1. an act or the privilege of going or coming back, reentry 1, movement backward to a previous and especially worse or more primitive state or condition, the act of reasoning backward, II.
Date: 1552
intransitive verb
1. to make or undergo regress ; retrograde , to be subject to or exhibit regression, to tend to approach or revert to a mean, transitive verb to induce a state of psychological regression in, regressor noun