horse fly vs cleg

horse fly and cleg both are nouns.

Word	Noun	Adjective	Verb	Adverb
horse fly	Yes	No	No	No
cleg	Yes	No	No	No

As nouns, horse fly and cleg are synonyms defined as:

horse fly and cleg: large swift fly the female of which sucks blood of various animals

Other synonyms of horse fly include clegg, horsefly.

horse fly (noun)	cleg (noun)
large swift fly the female of which sucks blood of various animals	large swift fly the female of which sucks blood of various animals