The Collaborative International Dictionary of English v.0.48:

Sixteenth \Six"teenth`\, a. [From Sixteen: cf. AS.
   sixte['o]?a.]
   1. Sixth after the tenth; next in order after the fifteenth.
      [1913 Webster]

   2. Constituting or being one of sixteen equal parts into
      which anything is divided.
      [1913 Webster]

   Sixteenth note (Mus.), the sixteenth part of a whole note;
      a semiquaver.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sixteenth \Six"teenth`\, n.
   1. The quotient of a unit divided by sixteen; one of sixteen
      equal parts of one whole.
      [1913 Webster]

   2. The next in order after the fifteenth; the sixth after the
      tenth.
      [1913 Webster]

   3. (Mus.) An interval comprising two octaves and a second.
      --Moore (Encyc. of Music.)
      [1913 Webster]

WordNet (r) 3.0 (2006):

sixteenth
    adj 1: coming next after the fifteenth in position [syn:
           sixteenth, 16th]
    n 1: position 16 in a countable series of things
    2: one part in sixteen equal parts [syn: one-sixteenth,
       sixteenth, sixteenth part]