Source : Webster's Revised Unabridged Dictionary (1913)

Eleventh \E*lev"enth\, a. [Cf. AS. endlyfta. See {Eleven}.]
   1. Next after the tenth; as, the eleventh chapter.

   2. Constituting one of eleven parts into which a thing is
      divided; as, the eleventh part of a thing.

   3. (Mus.) Of or pertaining to the interval of the octave and
      the fourth.

Eleventh \E*lev"enth\, n.
   1. The quotient of a unit divided by eleven; one of eleven
      equal parts.

   2. (Mus.) The interval consisting of ten conjunct degrees;
      the interval made up of an octave and a fourth.

Source : WordNet®

eleventh
     n : position 11 in a countable series of things

eleventh
     adj : coming next after the tenth and just before the twelfth in
           position [syn: {11th}]