hind limb vs hindlimb

hind limb and hindlimb both are nouns.

Word	Noun	Adjective	Verb	Adverb
hind limb	Yes	No	No	No
hindlimb	Yes	No	No	No

As nouns, hind limb and hindlimb are synonyms defined as:

hind limb and hindlimb: a posterior appendage such as a leg or the homologous structure in other animals

hind limb (noun)	hindlimb (noun)
a posterior appendage such as a leg or the homologous structure in other animals	a posterior appendage such as a leg or the homologous structure in other animals