Definition of "Fellow" :

noun: a man who is the lover of a man or woman

noun: a boy or man

"There's a fellow at the door."

noun: a person who is member of one's class or profession

"He sent e-mail to his fellow hackers."

noun: a friend who is frequently in the company of another

noun: an informal form of address for a man

"Say, fellow, what are you doing?."

noun: a member of a learned society

"He was elected a fellow of the American Physiological Association."

noun: one of a pair

"One eye was blue but its fellow was brown."