Source : Webster's Revised Unabridged Dictionary (1913)

Twelfth \Twelfth\, a. [For twelft, OE. twelfte, AS. twelfta. See
   {Twelve}.]
   1. Next in order after the eleventh; coming after eleven
      others; -- the ordinal of twelve.

   2. Consisting, or being one of, twelve equal parts into which
      anything is divided.

Twelfth \Twelfth\, n.
   1. The quotient of a unit divided by twelve; one of twelve
      equal parts of one whole.

   2. The next in order after the eleventh.

   3. (Mus.) An interval comprising an octave and a fifth.

Source : WordNet®

twelfth
     n : position 12 in a countable series of things

twelfth
     adj : coming next after the eleventh and just before the
           thirteenth in position [syn: {12th}]