Definition of "Reversion" :

noun: a failure to maintain a higher state

noun: returning to a former state

noun: turning in the opposite direction

noun: a reappearance of an earlier characteristic

noun: (genetics) a return to a normal phenotype (usually resulting from a second mutation)

noun: (law) an interest in an estate that reverts to the grantor (or his heirs) at the end of some period (e.g., the death of the grantee)