Source : Webster's Revised Unabridged Dictionary (1913)

Eighth \Eighth\, a. [AS. eahto?a.]
   1. Next in order after the seventh.

   2. Consisting of one of eight equal divisions of a thing.

   {Eighth note} (Mus.), the eighth part of a whole note, or
      semibreve; a quaver.

Eighth \Eighth\, n.
   1. The quotient of a unit divided by eight; one of eight
      equal parts; an eighth part.

   2. (Mus.) The interval of an octave.

Source : WordNet®

eighth
     adj : coming next after the seventh and just before the ninth in
           position [syn: {8th}]

eighth
     n 1: position eight in a countable series of things
     2: an eighth part [syn: {one-eighth}]