What is "to revert a series"

Revert \Re*vert"\, v. t. [imp. & p. p. Reverted; p. pr. & vb. n. Reverting.] [L. revertere, reversum; pref. re- re- + vertere to turn: cf. OF. revertir. See Verse, and cf. Reverse.]

1. To turn back, or to the contrary; to reverse.

   Till happy chance revert the cruel scence.
   --Prior.

   The tumbling stream . . . Reverted, plays in undulating flow.
   --Thomson.

2. To throw back; to reflect; to reverberate.

3. (Chem.) To change back. See Revert, v. i.

   To revert a series (Alg.), to treat a series, as y = a + bx + cx^ 2 + 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.