muscle builder vs musclebuilder

muscle builder and musclebuilder both are nouns.

Word	Noun	Adjective	Verb	Adverb
muscle builder	Yes	No	No	No
musclebuilder	Yes	No	No	No

As nouns, muscle builder and musclebuilder are synonyms defined as:

muscle builder and musclebuilder: someone who does special exercises to develop a brawny musculature

Other synonyms of muscle builder include bodybuilder, muscle-builder, muscleman.

muscle builder (noun)	musclebuilder (noun)
someone who does special exercises to develop a brawny musculature	someone who does special exercises to develop a brawny musculature