dumbbell vs pinhead

dumbbell and pinhead both are nouns.

Word	Noun	Adjective	Verb	Adverb
dumbbell	Yes	No	No	No
pinhead	Yes	No	No	No

As nouns, dumbbell and pinhead are synonyms defined as:

Other synonyms of dumbbell include boob, booby, dope, dummy.

dumbbell (noun)	pinhead (noun)
an exercising weight; two spheres connected by a short bar that serves as a handle	the head of a pin
an ignorant or foolish person	an ignorant or foolish person