Source : Webster's Revised Unabridged Dictionary (1913)

Behind \Be*hind"\, prep. [AS. behindan; pref. be- + hindan. See
   {Hind}, a.]
   1. On the side opposite the front or nearest part; on the
      back side of; at the back of; on the other side of; as,
      behind a door; behind a hill.

            A tall Brabanter, behind whom I stood. --Bp. Hall.

   2. Left after the departure of, whether this be by removing
      to a distance or by death.

            A small part of what he left behind him. --Pope.

   3. Left a distance by, in progress of improvement Hence:
      Inferior to in dignity, rank, knowledge, or excellence, or
      in any achievement.

            I was not a whit behind the very chiefest apostles.
                                                  --2 Cor. xi.
                                                  5.

Behind \Be*hind"\, adv.
   1. At the back part; in the rear. ``I shall not lag behind.''
      --Milton.

   2. Toward the back part or rear; backward; as, to look
      behind.

   3. Not yet brought forward, produced, or exhibited to view;
      out of sight; remaining.

            We can not be sure that there is no evidence behind.
                                                  --Locke.

   4. Backward in time or order of succession; past.

            Forgetting those things which are behind. --Phil.
                                                  ii. 13.

   5. After the departure of another; as, to stay behind.

            Leave not a rack behind.              --Shak.

Behind \Be*hind"\, n.
   The backside; the rump. [Low]

Source : WordNet®

behind
     n : the fleshy part of the human body that you sit on; "he
         deserves a good kick in the butt"; "are you going to sit
         on your fanny and do nothing?" [syn: {buttocks}, {nates},
          {arse}, {butt}, {backside}, {bum}, {buns}, {can}, {fundament},
          {hindquarters}, {hind end}, {keister}, {posterior}, {prat},
          {rear}, {rear end}, {rump}, {stern}, {seat}, {tail}, {tail
         end}, {tooshie}, {tush}, {bottom}, {derriere}, {fanny}, {ass}]
     adv 1: in or to or toward the rear; "he followed behind"; "seen
            from behind, the house is more imposing than it is
            from the front"; "the final runners were far behind"
     2: remaining in a place or condition that has been left or
        departed from; "when he died he left much unfinished work
        behind"; "left a large family behind"; "the children left
        their books behind"; "he took off with a squeal of tires
        and left the other cars far behind"
     3: of timepieces; "the clock is almost an hour slow"; "my watch
        is running behind" [syn: {slow}]
     4: in or into an inferior position; "fell behind in his
        studies"; "their business was lagging behind in the
        competition for customers"
     5: in debt; "he fell behind with his mortgage payments"; "a
        month behind in the rent"; "a company that has been run
        behindhand for years"; "in arrears with their utility
        bills" [syn: {behindhand}, {in arrears}]

behind
     adj : having the lower score or lagging position in a contest;
           "behind by two points"; "the 8th inning found the home
           team trailing" [syn: {behind(p)}, {trailing}]