英汉词典

1. 武断的;任意的;任性的;主观的
    If you describe an action, rule, or decision as arbitrary, you think that it is not based on any principle, plan, or system. It often seems unfair because of this.

    e.g. Arbitrary arrests and detention without trial were common.
           随意逮捕和拘留屡见不鲜。