The epitome of a friend. Somebody you kick it with. A person who always has your back. You can't go through life without a homeboy. It's hard to have more than one, because they're one in a million.
Originally used among transplanted African-Americans with Southern roots to refer to and aid in the assimilation of someone who might have directly migrated from a common Southern home town or is otherwise well known to the person using the term.
Used to establish a mutual relationship between the invidividual using the term, the person described by it, and a third person.
Contrary to popular belief, homeboy along with homie were both created by Chicano aka Mexican American Pachucos from the word "Hombre" which is spanish for "man". It all derived from the slang they used known as "Calo".