The Collaborative International Dictionary of English v.0.48:

Tenth \Tenth\, n.
   1. The next in order after the ninth; one coming after nine
      others.
      [1913 Webster]

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

   3. The tenth part of annual produce, income, increase, or the
      like; a tithe. --Shak.
      [1913 Webster]

   4. (Mus.) The interval between any tone and the tone
      represented on the tenth degree of the staff above it, as
      between one of the scale and three of the octave above;
      the octave of the third.
      [1913 Webster]

   5. pl. (Eng. Law)
      (a) A temporary aid issuing out of personal property, and
          granted to the king by Parliament; formerly, the real
          tenth part of all the movables belonging to the
          subject.
      (b) (Eccl. Law) The tenth part of the annual profit of
          every living in the kingdom, formerly paid to the
          pope, but afterward transferred to the crown. It now
          forms a part of the fund called Queen Anne's Bounty.
          --Burrill.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tenth \Tenth\ (t[e^]nth), a. [From Ten: cf. OE. tethe, AS.
   te['o][eth]a. See Ten, and cf. Tithe.]
   1. Next in order after the ninth; coming after nine others.
      [1913 Webster]

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

WordNet (r) 3.0 (2006):

tenth
    adj 1: coming next after the ninth and just before the eleventh
           in position [syn: tenth, 10th]
    n 1: a tenth part; one part in ten equal parts [syn: one-
         tenth, tenth, tenth part, ten percent]
    2: position ten in a countable series of things