Wordnet 3.0
NOUN (1)
1. 
 an adherent of Sikhism; 
ADJECTIVE (1)
1. 
 of or relating to the Sikhs or their religious beliefs and customs; 
The Collaborative International Dictionary of English v.0.48:
Sikhs \Sikhs\, n. pl.; sing. Sikh. [Hind. Sikh, properly, a
   disciple.]
   A religious sect noted for warlike traits, founded in the
   Punjab at the end of the 15th century.
   [1913 Webster]
WordNet (r) 3.0 (2006):
Sikh
    adj 1: of or relating to the Sikhs or their religious beliefs
           and customs
    n 1: an adherent of Sikhism