You're shunned by the greater public, typically due to upsetting some social order or causing some form of trouble which leaves you an outlaw. Whether or not you're pursued legally, you're operating at the bottom rung of society currently - whether by choice or not.
You receive a +5 bonus to all social skill check with other outcasts or characters from the Vagabond Occupations, and a -5 penalty with regular law-abiding citizens and nobility.