The Collaborative International Dictionary of English v.0.48:

Unrelated \Unrelated\
   See related.

WordNet (r) 3.0 (2006):

unrelated
    adj 1: lacking a logical or causal relation [ant: related,
           related to]
    2: not connected by kinship [ant: related]

Moby Thesaurus II by Grady Ward, 1.0:

35 Moby Thesaurus words for "unrelated":
   alien, apart, detached, different, disconnected, discrete,
   disjunct, disrelated, dissimilar, dissociated, distinct, exotic,
   extraneous, foreign, inappropriate, incommensurable, incomparable,
   incompatible, independent, insular, irrelative, isolated, other,
   outlandish, removed, segregate, separate, separated, strange,
   unaffiliated, unallied, unassociated, unconnected, unlinked,
   unrelatable