A "Jabba" is in reference to "Jabba The Hut" from star wars. This fat, slobbish persn has little respect for their personal appearance and lacks the motivation to put out the minimal effort it takes to roll off of the couch. A slobish, obese brute. Can be found sleeping on the couch watching daytime tv with half eaten sandwiches on his gut. Sometime Jabbas are prone to smell of feces and filth from either defecating themselves or continuos farting.
When an unfamiliar friend stops by your house and ghasps, " What the fuck is that thing on the couch?" You can reply, "Oh that's just Jabba, he doesn't do much of anything, sorry about the smell though."