Source : Webster's Revised Unabridged Dictionary (1913)

Tail \Tail\, n. [AS. t[ae]gel, t[ae]gl; akin to G. zagel, Icel.
   tagl, Sw. tagel, Goth. tagl hair. [root]59.]
   1. (Zo["o]l.) The terminal, and usually flexible, posterior
      appendage of an animal.

   Note: The tail of mammals and reptiles contains a series of
         movable vertebr[ae], and is covered with flesh and
         hairs or scales like those of other parts of the body.
         The tail of existing birds consists of several more or
         less consolidated vertebr[ae] which supports a fanlike
         group of quills to which the term tail is more
         particularly applied. The tail of fishes consists of
         the tapering hind portion of the body ending in a
         caudal fin. The term tail is sometimes applied to the
         entire abdomen of a crustacean or insect, and sometimes
         to the terminal piece or pygidium alone.

   2. Any long, flexible terminal appendage; whatever resembles,
      in shape or position, the tail of an animal, as a catkin.

            Doretus writes a great praise of the distilled
            waters of those tails that hang on willow trees.
                                                  --Harvey.

   3. Hence, the back, last, lower, or inferior part of
      anything, -- as opposed to the {head}, or the superior
      part.

            The Lord will make thee the head, and not the tail.
                                                  --Deut.
                                                  xxviii. 13.

   4. A train or company of attendants; a retinue.

            ``Ah,'' said he, ``if you saw but the chief with his
            tail on.''                            --Sir W.
                                                  Scott.

   5. The side of a coin opposite to that which bears the head,
      effigy, or date; the reverse; -- rarely used except in the
      expression ``heads or tails,'' employed when a coin is
      thrown up for the purpose of deciding some point by its
      fall.

   6. (Anat.) The distal tendon of a muscle.

   7. (Bot.) A downy or feathery appendage to certain achenes.
      It is formed of the permanent elongated style.

   8. (Surg.)
      (a) A portion of an incision, at its beginning or end,
          which does not go through the whole thickness of the
          skin, and is more painful than a complete incision; --
          called also {tailing}.
      (b) One of the strips at the end of a bandage formed by
          splitting the bandage one or more times.

   9. (Naut.) A rope spliced to the strap of a block, by which
      it may be lashed to anything.

   10. (Mus.) The part of a note which runs perpendicularly
       upward or downward from the head; the stem. --Moore
       (Encyc. of Music).

   11. pl. Same as {Tailing}, 4.

   12. (Arch.) The bottom or lower portion of a member or part,
       as a slate or tile.

   13. pl. (Mining) See {Tailing}, n., 5.

   {Tail beam}. (Arch.) Same as {Tailpiece}.

   {Tail coverts} (Zo["o]l.), the feathers which cover the bases
      of the tail quills. They are sometimes much longer than
      the quills, and form elegant plumes. Those above the
      quills are called the {upper tail coverts}, and those
      below, the {under tail coverts}.

   {Tail end}, the latter end; the termination; as, the tail end
      of a contest. [Colloq.]

   {Tail joist}. (Arch.) Same as {Tailpiece}.

   {Tail of a comet} (Astron.), a luminous train extending from
      the nucleus or body, often to a great distance, and
      usually in a direction opposite to the sun.

   {Tail of a gale} (Naut.), the latter part of it, when the
      wind has greatly abated. --Totten.

   {Tail of a lock} (on a canal), the lower end, or entrance
      into the lower pond.

   {Tail of the trenches} (Fort.), the post where the besiegers
      begin to break ground, and cover themselves from the fire
      of the place, in advancing the lines of approach.

   {Tail spindle}, the spindle of the tailstock of a turning
      lathe; -- called also {dead spindle}.

   {To turn tail}, to run away; to flee.

            Would she turn tail to the heron, and fly quite out
            another way; but all was to return in a higher
            pitch.                                --Sir P.
                                                  Sidney.

Source : WordNet®

tail end
     n 1: the time of the last part of something; "the fag end of this
          crisis-ridden century"; "the tail of the storm" [syn: {fag
          end}, {tail}]
     2: any projection that resembles the tail of an animal [syn: {tail}]
     3: 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}, {tooshie},
         {tush}, {bottom}, {behind}, {derriere}, {fanny}, {ass}]