Faire la grasse matinée has long been one of my all time favorite French expressions. The literal meaning if this idiom is “to make the fat morning” and the meaning is to sleep in or to sleep late.
A French-to-French definition could be rester au lit jusqu’au très tard, or to stay in bed until very late.
The word “gras” is both a noun and adjective meaning fat and fatty, respectively.
Here are some example sentences:
- Le dimanche je fais la grasse matinée et je me lève tres tard. On Sundays I sleep in and wake up very late.
- Il est rare que je fasse le grasse matinée car je préfère me lever tot. It’s rare that I sleep in because I prefer to wake up early.