old man vs USA

old man and USA both are nouns.

Word	Noun	Adjective	Verb	Adverb
old man	Yes	No	No	No
USA	Yes	No	No	No

old man (noun)	USA (noun)
an informal term for your father	the army of the United States of America; the agency that organizes and trains soldiers for land warfare
a man who is very old	North American republic containing 50 states - 48 conterminous states in North America plus Alaska in northwest North America and the Hawaiian Islands in the Pacific Ocean; achieved independence in 1776
a familiar term of address for a man
(slang) boss
aromatic herb of temperate Eurasia and North Africa having a bitter taste used in making the liqueur absinthe