Arbitrary means based on chance or personal power, not reason or rules. Learn how to use this adjective in different contexts with synonyms, antonyms, and examples from the Cambridge Dictionary. ' Arbitrary ' means based on random choice or personal whim, rather than any reason or system. It can also describe someone who exercises unrestrained and autocratic authority. arbitrary meaning , definition , what is arbitrary : decided or arranged without any reason o...: Learn more. Definition of arbitrary adjective from the Oxford Advanced Learner's Dictionary. (of an action, a decision, a rule, etc.) not seeming to be based on a reason, system or plan and sometimes seeming unfair. The choice of players for the team seemed completely arbitrary . He makes unpredictable, arbitrary decisions.
