Someone who exemplifies all the qualities typically associated with people who carry themselves without any taste or class or tact. Also applies to someone who enthusiastically subscribes to the working class, or street thug lifestyle. The word originates from Pacheco, a dowtrodden suburb of Concord, CA. Often the term is used by upwardly mobile snobby types who want to discreetly mock those in their midst who they view as below them in the social order.
Check out that total chooker at the bar, smoking her Marlboro Lights 100s. Not only are her acid wash jeans painted on, but I bet she left the T-Tops on her Trans-Am tonite because she didn't want to mess up her feathered, Aquanet hair.