motion that continues indefinitely without any external source of energy; impossible in practice because of friction
双语例句
用作名词 (n.)
My organ grinder has discovered the miracle of perpetual motion.Round and round goes his arm, his body rocking to the effort. 我那位演奏风琴的艺人已发现了永恒运动的奥秘，他的手不断地拉来拉去，身体也随音乐摇晃。
