Nouns

(n)reversion(law) an interest in an estate that reverts to the grantor (or their heirs) at the end of some period (e.g., the death of the grantee)
(n)reversion(genetics) a return to a normal phenotype (usually resulting from a second mutation)
(n)atavism, reversion, throwbacka reappearance of an earlier characteristic
(n)reversion, reverse, reversal, turnabout, turnaroundturning in the opposite direction
(n)backsliding, lapse, lapsing, relapse, relapsing, reversion, revertinga failure to maintain a higher state