regio
nounEtymology Learned borrowing from Latin regiō. Doublet of region.
1
Astronomy, Geography, Geology, Natural sciences Any large area of a planet or moon that is strongly differentiated from neighbouring areas by colour or albedo.
Planetary geology
2
Ancient Rome A district of a city.
- The British School has unearthed a city of continuous houses, more than 400 feet long by 350 broad, whose many blocks or "insul[ae]" might seem almost to need the more elaborate grouping of the "regiones" of Pompeii.1907, Ronald M. Burrows, The Discoveries In Crete, page 27: