Merriam-Webster Collegiate Dictionary - regress

 I. noun  Etymology: Middle English ~e, from Anglo-French, from Latin ~us, from regredi to go back, from re- + gradi to go — more at grade  Date: 14th century  1.  a. an act or the privilege of going or coming back  b. reentry 1  2. movement backward to a previous and especially worse or more primitive state or condition  3. the act of reasoning backward  II. Date: 1552  intransitive verb  1.  a. to make or undergo ~ ; retrograde  b. to be subject to or exhibit ~ion  2. to tend to approach or revert to a mean  transitive verb to induce a state of psychological ~ion in  • ~or noun