Source : Webster's Revised Unabridged Dictionary (1913)

Seventeenth \Sev"en*teenth`\, a. [From {Seventeen}: cf. AS.
   seofonte['o][eth]a, seofonteoge[eth]a.]
   1. Next in order after the sixteenth; coming after sixteen
      others.

            In . . . the seventeenth day of the month . . . were
            all the fountains of the great deep broken up.
                                                  --Gen. vii.
                                                  11.

   2. Constituting or being one of seventeen equal parts into
      which anything is divided.

Seventeenth \Sev"en*teenth`\, n.
   1. The next in order after the sixteenth; one coming after
      sixteen others.

   2. The quotient of a unit divided by seventeen; one of
      seventeen equal parts or divisions of one whole.

   3. (Mus.) An interval of two octaves and a third.

Source : WordNet®

seventeenth
     adj : coming next after the sixteenth in position [syn: {17th}]
     n : position 17 in a countable series of things