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to oversleep; to sleep late in the morning. If you sleep in again, you'll get fired. I really felt like sleeping in this morning.
1. Sleep at one's place of employment, as in They have a butler and maid who both sleep in. [First half of 1800s]
2. Sleep late, either accidentally or deliberately. For example, I slept in and missed my usual train, or On weekends we like to sleep in. [Late 1800s]
1. To oversleep: I missed the morning train because I slept in.
2. To sleep late on purpose: After this week's work, I will sleep in on Saturday.
3. To sleep at one's place of employment: Their nanny sleeps in so she can take care of the children at night.