The Collaborative International Dictionary of English v.0.48:

Uncaused \Un*caused"\, a.
   Having no antecedent cause; uncreated; self-existent;
   eternal. --A. Baxter.
   [1913 Webster]

WordNet (r) 3.0 (2006):

uncaused
    adj 1: having no cause or apparent cause; "a causeless miracle";
           "fortuitous encounters--strange accidents of fortune";
           "we cannot regard artistic invention as...uncaused and
           unrelated to the times" [syn: causeless, fortuitous,
           uncaused]

Moby Thesaurus II by Grady Ward, 1.0:

28 Moby Thesaurus words for "uncaused":
   accidental, adventitious, aleatory, casual, causeless, chance,
   chancy, contingent, destinal, dicey, fatal, fatidic, fluky,
   fortuitous, iffy, incidental, increate, indeterminate, risky,
   self-existing, unbegotten, uncreated, undetermined, unexpected,
   unforeseeable, unforeseen, unlooked-for, unpredictable