a response given to thwart the continuance of a conversation due lack of interest, lack of substance, lack of agreement, etc. Not necessarily negitvely connotative, often used playfully. Used to replace "no", "not right now", "not really", "I don't wanna"
-Yo dude you wanna go to a karaoke bar tonight?
-Aba
-Dude I was fuckin wasted but I'm pretty surethat chick I nailed last night wasn't that bad looking. Should I call her tonight to come hang out with us?
-Aba
-I'm thinkin about growing a goatee. That would be pretty sweet. Right?
-Aba