mean and poor both are nouns.

mean and poor both are adjectives.

mean is a verb but poor is not a verb.

mean (noun)	poor (noun)
an average of n numbers computed by adding some function of the numbers and dividing by some function of n	people without possessions or wealth (considered as a group)

mean (adjective)	poor (adjective)
approximating the statistical norm or average or expected value	having little money or few possessions
characterized by malice	characterized by or indicating poverty
having or showing an ignoble lack of honor or morality	lacking in quality or substances
marked by poverty befitting a beggar	deserving or inciting pity
(used of persons or behavior) characterized by or indicative of lack of generosity	of insufficient quantity to meet a need
(used of sums of money) so small in amount as to deserve contempt
of no value or worth
very good; of the highest quality

mean (verb)	poor (verb)
mean or intend to express or convey
have as a logical consequence
denote or connote
have in mind as a purpose
have a specified degree of importance
intend to refer to
destine or designate for a certain purpose