The Collaborative International Dictionary of English v.0.48:

Seventh \Sev"enth\, a. [From Seven: cf. AS. seofo[eth]a.]
   1. Next in order after the sixth;; coming after six others.
      [1913 Webster]

            On the seventh day, God ended his work which he had
            made; and he rested on the seventh day from all his
            work which he had made.               --Gen. ii. 2.
      [1913 Webster]

   2. Constituting or being one of seven equal parts into which
      anything is divided; as, the seventh part.
      [1913 Webster]

   Seventh day, the seventh day of the week; Saturday.

   Seventh-day Baptists. See under Baptist.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Seventh \Sev"enth\, n.
   1. One next in order after the sixth; one coming after six
      others.
      [1913 Webster]

   2. The quotient of a unit divided by seven; one of seven
      equal parts into which anything is divided.
      [1913 Webster]

   3. (Mus.)
      (a) An interval embracing seven diatonic degrees of the
          scale.
      (b) A chord which includes the interval of a seventh
          whether major, minor, or diminished.
          [1913 Webster]

WordNet (r) 3.0 (2006):

seventh
    adj 1: coming next after the sixth and just before the eighth in
           position [syn: seventh, 7th]
    n 1: position seven in a countable series of things
    2: one part in seven equal parts [syn: one-seventh, seventh]
    3: the musical interval between one note and another seven notes
       away from it