donjon vs Black Hole of Calcutta

donjon and Black Hole of Calcutta both are nouns.

Word	Noun	Adjective	Verb	Adverb
donjon	Yes	No	No	No
Black Hole of Calcutta	Yes	No	No	No

donjon (noun)	Black Hole of Calcutta (noun)
the main tower within the walls of a medieval castle or fortress	a dungeon (20 feet square) in a fort in Calcutta where as many as 146 English prisoners were held overnight by Siraj-ud-daula; the next morning only 23 were still alive