The Collaborative International Dictionary of English v.0.48:

Gain \Gain\, v. t. [imp. & p. p. Gained (g[=a]nd); p. pr. &
   vb. n. Gaining.] [From gain, n. but. prob. influenced by F.
   gagner to earn, gain, OF. gaaignier to cultivate, OHG.
   weidin[=o]n, weidinen to pasture, hunt, fr. weida pasturage,
   G. weide, akin to Icel. vei[eth]r hunting, AS. w[=a][eth]u,
   cf. L. venari to hunt, E. venison. See Gain, n., profit.]
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   1. To get, as profit or advantage; to obtain or acquire by
      effort or labor; as, to gain a good living.
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            What is a man profited, if he shall gain the whole
            world, and lose his own soul?         --Matt. xvi.
                                                  26.
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            To gain dominion, or to keep it gained. --Milton.
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            For fame with toil we gain, but lose with ease.
                                                  --Pope.
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   2. To come off winner or victor in; to be successful in; to
      obtain by competition; as, to gain a battle; to gain a
      case at law; to gain a prize.
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   3. To draw into any interest or party; to win to one's side;
      to conciliate.
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            If he shall hear thee, thou hast gained thy brother.
                                                  --Matt. xviii.
                                                  15.
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            To gratify the queen, and gained the court.
                                                  --Dryden.
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   4. To reach; to attain to; to arrive at; as, to gain the top
      of a mountain; to gain a good harbor.
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            Forded Usk and gained the wood.       --Tennyson.
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   5. To get, incur, or receive, as loss, harm, or damage. [Obs.
      or Ironical]
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            Ye should . . . not have loosed from Crete, and to
            have gained this harm and loss.       --Acts xxvii.
                                                  21.
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   Gained day, the calendar day gained in sailing eastward
      around the earth.

   To gain ground, to make progress; to advance in any
      undertaking; to prevail; to acquire strength or extent.

   To gain over, to draw to one's party or interest; to win
      over.

   To gain the wind (Naut.), to reach the windward side of
      another ship.

   Syn: To obtain; acquire; get; procure; win; earn; attain;
        achieve.

   Usage: See Obtain. -- To Gain, Win. Gain implies only
          that we get something by exertion; win, that we do it
          in competition with others. A person gains knowledge,
          or gains a prize, simply by striving for it; he wins a
          victory, or wins a prize, by taking it in a struggle
          with others.
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