bed bug vs bedbug

bed bug and bedbug both are nouns.

Word	Noun	Adjective	Verb	Adverb
bed bug	Yes	No	No	No
bedbug	Yes	No	No	No

As nouns, bed bug and bedbug are synonyms defined as:

bed bug and bedbug: bug of temperate regions that infests especially beds and feeds on human blood

Other synonyms of bed bug include chinch, Cimex lectularius.

bed bug (noun)	bedbug (noun)
bug of temperate regions that infests especially beds and feeds on human blood	bug of temperate regions that infests especially beds and feeds on human blood