Source : Webster's Revised Unabridged Dictionary (1913)

Back \Back\, adv. [Shortened from aback.]
   1. In, to, or toward, the rear; as, to stand back; to step
      back.

   2. To the place from which one came; to the place or person
      from which something is taken or derived; as, to go back
      for something left behind; to go back to one's native
      place; to put a book back after reading it.

   3. To a former state, condition, or station; as, to go back
      to private life; to go back to barbarism.

   4. (Of time) In times past; ago. ``Sixty or seventy years
      back.'' --Gladstone.

   5. Away from contact; by reverse movement.

            The angel of the Lord . . . came, and rolled back
            the stone from the door.              --Matt. xxvii.
                                                  2.

   6. In concealment or reserve; in one's own possession; as, to
      keep back the truth; to keep back part of the money due to
      another.

   7. In a state of restraint or hindrance.

            The Lord hath kept thee back from honor. --Numb.
                                                  xxiv. 11.

   8. In return, repayment, or requital.

            What have I to give you back!         --Shak.

   9. In withdrawal from a statement, promise, or undertaking;
      as, he took back0 the offensive words.

   10. In arrear; as, to be back in one's rent. [Colloq.]

   {Back and forth}, backwards and forwards; to and fro.

   {To go back on}, to turn back from; to abandon; to betray;
      as, to go back on a friend; to go back on one's
      professions. [Colloq.]

Forth \Forth\, v.[AS. for[eth], fr. for akin to D. voort, G.
   fort [root]78. See {Fore}, {For}, and cf. {Afford},
   {Further}, adv.]
   1. Forward; onward in time, place, or order; in advance from
      a given point; on to end; as, from that day forth; one,
      two, three, and so forth.

            Lucas was Paul's companion, at the leastway from the
            sixteenth of the Acts forth.          --Tyndale.

            From this time forth, I never will speak word.
                                                  --Shak.

            I repeated the Ave Maria; the inquisitor bad me say
            forth; I said I was taught no more.   --Strype.

   2. Out, as from a state of concealment, retirement,
      confinement, nondevelopment, or the like; out into notice
      or view; as, the plants in spring put forth leaves.

            When winter past, and summer scarce begun, Invites
            them forth to labor in the sun.       --Dryden.

   3. Beyond a (certain) boundary; away; abroad; out.

            I have no mind of feasting forth to-night. --Shak.

   4. Throughly; from beginning to end. [Obs.] --Shak.

   {And so forth}, {Back and forth}, {From forth}. See under
      {And}, {Back}, and {From}.

   {Forth of}, {Forth from}, out of. [Obs.] --Shak.

   {To bring forth}. See under {Bring}.

Source : WordNet®

back and forth
     adv : moving from one place to another and back again; "he
           traveled back and forth between Los Angeles and New
           York" [syn: {backward and forward}, {to and fro}]