A shit talker is what 99% of people under25 years of age are, especially when around other "shit talkers" who like try try to impress other idiots of their age group, to try to appear "worldly" or "knowledgeable" about something they know absolutely nothing about. Shit talkers are silent around adults, (people over 35) because they realize that people who have lived a while have heard plenty of bullshit talk and are not impressed by juveniles babbling bullshit.
See also: liar, punk.
A black or white shit talker is generally a wannabe gangster, because they need a group of people around them to back up their mouth, and to feel like they're "tough" All gang members are "shit talkers".
Anyone of any color or nationality who was born and raised in America, but completely failed at reading writing and speaking the english language. One who speaks nothing but ebonics, has little if any education, discipline or common sense, and manages to sell his/her verbal feces to millions of other people who aspire to be like him/her.