causeless

Adjective
  1. Having no justifying cause or reason (synset 301563435)
    "a senseless, causeless murder"; "a causeless war that never had an aim"; "an apparently arbitrary and reasonless change"
  2. Having no cause or apparent cause (synset 301342240)
    "a causeless miracle"; "fortuitous encounters--strange accidents of fortune"; "we cannot regard artistic invention as...uncaused and unrelated to the times"

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