greybeard vs long-beard

greybeard and long-beard both are nouns.

Word	Noun	Adjective	Verb	Adverb
greybeard	Yes	No	No	No
long-beard	Yes	No	No	No

As nouns, greybeard and long-beard are synonyms defined as:

greybeard and long-beard: a stoneware drinking jug with a long neck; decorated with a caricature of Cardinal Bellarmine (17th century)

Other synonyms of greybeard include bellarmine, longbeard.

greybeard (noun)	long-beard (noun)
a stoneware drinking jug with a long neck; decorated with a caricature of Cardinal Bellarmine (17th century)	a stoneware drinking jug with a long neck; decorated with a caricature of Cardinal Bellarmine (17th century)
a man who is very old