What does "revert" mean?

Additional senses

1. 2.(Chem.) To change back. See Revert, v. i. To revert a series (Alg.), to treat a series, as y = a + bx + cx2 + etc., where one variable y is expressed in powers of a second variable x, so as to find therefrom the second variable x, expressed in a series arranged in powers of y.
2. 3.To return; to come back. So that my arrows Would have reverted to my bow again. Shak.
3. 4.(Law) To return to the proprietor after the termination of a particular estate granted by him.
4. 5.(Biol.) To return, wholly or in part, towards some preëxistent form; to take on the traits or characters of an ancestral type.
5. 6.(Chem.) To change back, as from a soluble to an insoluble state or the reverse; thus, phosphoric acid in certain fertilizers reverts.
6. 7.One who, or that which, reverts. An active promoter in making the East Saxons converts, or rather reverts, to the faith. Fuller.