moving or behaving in a way that is not regular, certain, or expected(动作、行为等)不规则的,不确定的,无计划的
He drove in an erratic course down the road.他开车忽左忽右地在路上行驶。
She can be very erratic; one day she is friendly and the next she'll hardly speak to you.她喜怒无常,今天待你很友好,明天又懒得理你。