slaw- terrible; slow, lazy, and/or weak
dogg- a term typically used to describe a close friend or homie, but in the case of a "slaw dogg", "dogg" simply refers to the person being described as "slaw"
So basically, a "slaw dogg" is a bitch ass motha fucka incapable of almost anything with the exception of distracting skeezers, skeelos, and on very rare occasions breelos from real ass niggas who could do they body right.
Look at that lil bitch. He's such a slaw dogg.