Wordnet 3.0
NOUN (1)
1. 
 one part in six equal parts; 
[syn: one-sixth, sixth]
The Collaborative International Dictionary of English v.0.48:
one-sixth \one-sixth\ n.
   a sixth part.
   Syn: sixth.
        [WordNet 1.5]
WordNet (r) 3.0 (2006):
one-sixth
    n 1: one part in six equal parts [syn: one-sixth, sixth]