Source : Webster's Revised Unabridged Dictionary (1913)

Better \Bet"ter\, a.; compar. of Good. [OE. betere, bettre, and
   as adv. bet, AS. betera, adj., and bet, adv.; akin to Icel.
   betri, adj., betr, adv., Goth. batiza, adj., OHG. bezziro,
   adj., baz, adv., G. besser, adj. and adv., bass, adv., E.
   boot, and prob. to Skr. bhadra excellent. See {Boot}
   advantage, and cf. {Best}, {Batful}.]
   1. Having good qualities in a greater degree than another;
      as, a better man; a better physician; a better house; a
      better air.

            Could make the worse appear The better reason.
                                                  --Milton.

   2. Preferable in regard to rank, value, use, fitness,
      acceptableness, safety, or in any other respect.

            To obey is better than sacrifice.     --1 Sam. xv.
                                                  22.

            It is better to trust in the Lord than to put
            confidence in princes.                --Ps. cxviii.
                                                  9.

   3. Greater in amount; larger; more.

   4. Improved in health; less affected with disease; as, the
      patient is better.

   5. More advanced; more perfect; as, upon better acquaintance;
      a better knowledge of the subject.

   {All the better}. See under {All}, adv.

   {Better half}, an expression used to designate one's wife.

            My dear, my better half (said he), I find I must now
            leave thee.                           --Sir P.
                                                  Sidney.

   {To be better off}, to be in a better condition.

   {Had better}. (See under {Had}).

   Note: The phrase had better, followed by an infinitive
         without to, is idiomatic. The earliest form of
         construction was ``were better'' with a dative; as,
         ``Him were better go beside.'' (--Gower.) i. e., It
         would be better for him, etc. At length the nominative
         (I, he, they, etc.) supplanted the dative and had took
         the place of were. Thus we have the construction now
         used.

               By all that's holy, he had better starve Than but
               once think this place becomes thee not. --Shak.

Half \Half\, n.; pl. {Halves}. [AS. healf. See {Half}, a.]
   1. Part; side; behalf. [Obs.] --Wyclif.

            The four halves of the house.         --Chaucer.

   2. One of two equal parts into which anything may be divided,
      or considered as divided; -- sometimes followed by of; as,
      a half of an apple.

            Not half his riches known, and yet despised.
                                                  --Milton.

            A friendship so complete Portioned in halves between
            us.                                   --Tennyson.

   {Better half}. See under {Better}.

   {In half}, in two; an expression sometimes used improperly
      instead of in or into halves; as, to cut in half.
      [Colloq.] --Dickens.

   {In, or On}, {one's half}, in one's behalf; on one's part.
      [Obs.]

   {To cry halves}, to claim an equal share with another.

   {To go halves}, to share equally between two.

Source : WordNet®

better half
     n : a person's partner in marriage [syn: {spouse}, {partner}, {married
         person}, {mate}]