black disease vs sheep rot

black disease and sheep rot both are nouns.

Word	Noun	Adjective	Verb	Adverb
black disease	Yes	No	No	No
sheep rot	Yes	No	No	No

As nouns, black disease and sheep rot are synonyms defined as:

black disease and sheep rot: a disease of the liver (especially in sheep and cattle) caused by liver flukes and their by-products

Other synonyms of black disease include distomatosis, liver rot.

black disease (noun)	sheep rot (noun)
a disease of the liver (especially in sheep and cattle) caused by liver flukes and their by-products	a disease of the liver (especially in sheep and cattle) caused by liver flukes and their by-products