stiff vs adult male

stiff and adult male both are nouns.

Word	Noun	Adjective	Verb	Adverb
stiff	Yes	Yes	No	Yes
adult male	Yes	No	No	No

As nouns, adult male is a hypernym of stiff; that is, adult male is a word with a broader meaning than stiff:

Other hypernyms of stiff include man.

stiff (noun)	adult male (noun)
the dead body of a human being	an adult person who is male (as opposed to a woman)
an ordinary man

stiff (adjective)	adult male (adjective)
having a strong physiological or chemical effect
rigidly formal
not moving or operating freely
very drunk
marked by firm determination or resolution; not shakable
strong, vigorous
incapable of or resistant to bending

stiff (adverb)	adult male (adverb)
in a stiff manner
to a great degree