Operate too slowly. For example, My watch loses time, or This clock loses five minutes a day. This usage is always applied to a timepiece. [Mid-1800s]
Waste time, delay, as in We wanted to paint the entire porch today, but we lost time trying to find a color that matched the house. This expression is sometimes put negatively as lose no time, meaning “act immediately” or “not delay,” as in We must lose no time in getting him to the hospital. [Late 1500s] Also see make up for lost time.