Contrefort-colonne (buttress column ©)

The translation in the title is followed by this sign ©; this means that it has been "invented" by me.

A colonne engagée (semicircular engaged column) or colonne adossée (semi-freestanding column) acting as a contrefort (buttress).
In the picture two contreforts-colonnes built aganst the déambulatoire (ambulatory) of the Notre-Dame-de-la-Nativité in Bois-Sainte-Marie.

Notre-Dame-de-la-Nativité - Bois-Sainte-Marie