Basically just a term for insulting, means the person you are insulting is retarded or just slow.

Special needs class. See also short bus.

A group of retards; could be used either referring the literal definition (I.E. severely physically/cognitively impaired individuals) or just a brigade of dumbasses. Sometimes extended to "Crayon Crunching Crew"—which adds emphasis to the fact that the people being referred to with such namesake are extra retarded.