Short term for "paisano" which translates to countryman.
An inhabitant of a rural or remote area who is usually characterized by an utter lack of sophistication and cultivation.
Usually mexicans from rural areas (like northern mexico) take this term as derogatory. To them it is like calling them "indigenous", "ignorant" and/or "flamboyant".
See also naco
People who are described as "paisas" usually love to listen to "quebradita" music which is the most hickish, disturbing music ever invented. They also speak very little English, which would be okay had they at least mastered the basics in Spanish--which most do not--and have a whiney voice when they do "speak" Spanish. They also claim to be very patriotic but hardly know anything about the history and culture of their country.