commander-in-chief vs generalissimo

commander-in-chief and generalissimo both are nouns.

Word	Noun	Adjective	Verb	Adverb
commander-in-chief	Yes	No	No	No
generalissimo	Yes	No	No	No

As nouns, commander-in-chief and generalissimo are synonyms defined as:

commander-in-chief and generalissimo: the officer who holds the supreme command

Other synonyms of commander-in-chief include commander in chief.

commander-in-chief (noun)	generalissimo (noun)
the officer who holds the supreme command	the officer who holds the supreme command