re·ver·sion 
(rĭ-vûrzhən)
(rĭ-vûrzhən)n.
1. A return to a former condition, belief, or interest.
2. A turning away or in the opposite direction; a reversal.
3. Genetics A return to the normal phenotype, usually by a second mutation.
4. Law
a. The return of an estate to the grantor or to the grantor's heirs or successor after the grant has expired.
b. The estate thus returned.
c. The right to succeed to such an estate.