(idiomatic) To sleep late; to go on sleeping past one's customary or planned hour.(verb)
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Use "sleep in" in a sentence
"After another good night of sleep in the dark Dolceacqua apartment, we enjoyed the traditional breakfast in the Bar California."
"Everyone is about to go to sleep in Novy Svet, the new world that suddenly feels so old."
"A solid nights sleep in a small ski hotel roofed with three-inch-thick slabs of granite, and the next day we made the curving ride back down to the highway."