Definition of "Rational" :

noun: an integer or a fraction

adjective: having its source in or being guided by the intellect (as distinguished from experience or emotion)

"A rational analysis."

adjective: of or associated with or requiring the use of the mind

"The triumph of the rational over the animal side of man."

adjective: consistent with or based on or using reason

"Rational behavior."

adjective: capable of being expressed as a quotient of integers

"Rational numbers."