Lazy Friendly Verb:
It is an abbreviation for "Can't be assed". It is generally used when you cannot be assed saying "I can't be assed".
Morons usually say: but cba should be short for "Can't be assed". But how would you pronounce cba? Not very useful word innit?
"Hey, can you put the light on?"
End of conversation.
"Do you wanna come out with me and Emma tonight?"
"Cab seeing that bitch again."