the act of turning something the reverse way.

the state of being so turned; reversal.

the act of reverting; return to a former practice, belief, condition, etc.

Biology .

reappearance of ancestral characters that have been absent in intervening generations.

return to an earlier or primitive type; atavism.

Law .

the returning of an estate to the grantor or the grantor's heirs after the interest granted expires.

an estate which so returns.

the right of succeeding to an estate.

Archaic . the remains, esp. of food or drink after a meal.

noun

regression , retrogradation , retrogression