Source : Webster's Revised Unabridged Dictionary (1913)

Believe \Be*lieve"\, v. t. [imp. & p. p. {Believed}; p. pr. &
   vb. n. {Believing}.] [OE. bileven (with pref. be- for AS.
   ge-), fr. AS. gel?fan, gel?fan; akin to D. gelooven, OHG.
   gilouban, G. glauben, OS. gil?bian, Goth. galaubjan, and
   Goth. liubs dear. See {Lief}, a., {Leave}, n.]
   To exercise belief in; to credit upon the authority or
   testimony of another; to be persuaded of the truth of, upon
   evidence furnished by reasons, arguments, and deductions of
   the mind, or by circumstances other than personal knowledge;
   to regard or accept as true; to place confidence in; to
   think; to consider; as, to believe a person, a statement, or
   a doctrine.

         Our conqueror (whom I now Of force believe almighty).
                                                  --Milton.

         King Agrippa, believest thou the prophets ? --Acts
                                                  xxvi. 27.

         Often followed by a dependent clause. I believe that
         Jesus Christ is the Son of God.          --Acts viii.
                                                  37.

   Syn: See {Expect}.

Believe \Be*lieve"\, v. i.
   1. To have a firm persuasion, esp. of the truths of religion;
      to have a persuasion approaching to certainty; to exercise
      belief or faith.

            Lord, I believe; help thou mine unbelief. --Mark ix.
                                                  24.

            With the heart man believeth unto righteousness.
                                                  --Rom. x. 10.

   2. To think; to suppose.

            I will not believe so meanly of you.  --Fielding.

   {To believe in}.
      (a) To believe that the subject of the thought (if a
          person or thing) exists, or (if an event) that it has
          occurred, or will occur; -- as, to believe in the
          resurrection of the dead. ``She does not believe in
          Jupiter.'' --J. H. Newman.
      (b) To believe that the character, abilities, and purposes
          of a person are worthy of entire confidence; --
          especially that his promises are wholly trustworthy.
          ``Let not your heart be troubled: ye believe in God,
          believe also in me.'' --John xiv. 1.
      (c) To believe that the qualities or effects of an action
          or state are beneficial: as, to believe in sea
          bathing, or in abstinence from alcoholic beverages.

   {To believe on}, to accept implicitly as an object of
      religious trust or obedience; to have faith in.

Source : WordNet®

believe
     v 1: accept as true; take to be true; "I believed his report";
          "We didn't believe his stories from the War"; "She
          believes in spirits" [ant: {disbelieve}]
     2: judge or regard; look upon; judge; "I think he is very
        smart"; "I believe her to be very smart"; "I think that he
        is her boyfriend"; "The racist conceives such people to be
        inferior" [syn: {think}, {consider}, {conceive}]
     3: be confident about something; "I believe that he will come
        back from the war" [syn: {trust}]
     4: follow a credo; have a faith; be a believer; "When you hear
        his sermons, you will be able to believe, too"
     5: credit with veracity; "You cannot believe this man"; "Should
        we believe a publication like the National Inquirer?"