Source : Webster's Revised Unabridged Dictionary (1913)

Posterior \Pos*te"ri*or\ (p[o^]s*t[=e]"r[i^]*[~e]r), a. [L.
   posterior, compar. of posterus coming after, from post after.
   See {Post-}.]
   1. Later in time; hence, later in the order of proceeding or
      moving; coming after; -- opposed to {prior}.

            Hesiod was posterior to Homer.        --Broome.

   2. Situated behind; hinder; -- opposed to {anterior}.

   3. (Anat.) At or toward the caudal extremity; caudal; -- in
      human anatomy often used for {dorsal}.

   4. (Bot.) On the side next the axis of inflorescence; -- said
      of an axillary flower. --Gray.

Source : WordNet®

posterior
     adj : at or near the hind end in quadrupeds or toward the spine in
           primates [ant: {anterior}]

posterior
     n 1: 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}, {prat}, {rear},
          {rear end}, {rump}, {stern}, {seat}, {tail}, {tail end},
           {tooshie}, {tush}, {bottom}, {behind}, {derriere}, {fanny},
           {ass}]
     2: a tooth situated at the back of the mouth [syn: {back tooth}]