If A and B are made of different power amps (separate amps inside) then that is Bi-Amping... but if A is just being paralleled to B then that will just be Bi-Wiring.
Cheers
Si Master Jojo naman eh, pumatol pa hehe, but I do have to correct myself, if powered by one amp it is bi-wiring indeed (bi-wiring has been shot down so many times I have trouble understanding why the term still exists in manuals!)
at the end of the day I think you want more power and if that's the case, using one amplifier for the job will not achieve that, kuha ka na lang ng power amp sir, and you wont need to bi-wire, that's almost certain.
You also mentioned that you do'nt want to have unused terminals at the back of you receiver, I think you might want to reconsider that thought, if you would check the specs of your receiver it would usually say XX wpc @ 2 channels driven, and it was discussed here before that as soon as you use the surround and the center terminals, that XX wpc goes down quite a bit.