1
general::
Phrase(s): sleep in
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.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
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]
American Heritage Idioms