up time

名词 up time:

1. a period of time when something (as a machine or factory) is functioning and available for use
   同义词：uptime

1. Activity, such as schoolwork or office work, meant to take up time but not necessarily yield productive results.
   无生产性工作，机关工作占用时间但不必要获得生产结果的活动，如学校工作或机关工作