arc-boutant vs buttressing

arc-boutant and buttressing both are nouns.

Word	Noun	Adjective	Verb	Adverb
arc-boutant	Yes	No	No	No
buttressing	Yes	No	No	No

As nouns, buttressing is a hypernym of arc-boutant; that is, buttressing is a word with a broader meaning than arc-boutant:

arc-boutant: a buttress that stands apart from the main structure and connected to it by an arch
buttressing: a support usually of stone or brick; supports the wall of a building

Other hypernyms of arc-boutant include buttress.

arc-boutant (noun)	buttressing (noun)
a buttress that stands apart from the main structure and connected to it by an arch	a support usually of stone or brick; supports the wall of a building