Source : Webster's Revised Unabridged Dictionary (1913)

Causeless \Cause"less\, a.
   1. Self-originating; uncreated.

   2. Without just or sufficient reason; groundless.

            My fears are causeless and ungrounded. --Denham.

Causeless \Cause"less\, adv.
   Without cause or reason.

Source : WordNet®

causeless
     adj 1: having no justifying cause or reason; "a senseless,
            causeless murder"; "a causeless war that never had an
            aim"; "an apparently arbitrary and reasonless change"
            [syn: {reasonless}]
     2: 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: {fortuitous}, {uncaused}]