The Collaborative International Dictionary of English v.0.48:

Gain \Gain\, v. i.
   To have or receive advantage or profit; to acquire gain; to
   grow rich; to advance in interest, health, or happiness; to
   make progress; as, the sick man gains daily.
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         Thou hast greedily gained of thy neighbors by
         extortion.                               --Ezek. xxii.
                                                  12.
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   Gaining twist, in rifled firearms, a twist of the grooves,
      which increases regularly from the breech to the muzzle.

   To gain on or To gain upon.
   (a) To encroach on; as, the ocean gains on the land.
   (b) To obtain influence with.
   (c) To win ground upon; to move faster than, as in a race or
       contest.
   (d) To get the better of; to have the advantage of.
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             The English have not only gained upon the Venetians
             in the Levant, but have their cloth in Venice
             itself.                              --Addison.
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             My good behavior had so far gained on the emperor,
             that I began to conceive hopes of liberty. --Swift.
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