1A very difficult or ambitious task.
2Philosophy a task (paradoxically) consisting of an infinite number of steps to be carried out within a finite period of time.
Early 20th century.
英语词典包含464360条英英释义在线翻译词条，基本涵盖了全部常用单词的英英翻译及用法，是英语学习的有利工具。