The act of using both hands and mouth in oral sex, the common usage of twucking is standing to the side of your partner, reaching around their back and groping her breast/pinching his nipple, while using the other hand to stimulate their crotch, the mouth being used for the other nipple.
If holding your partner slightly of fully suspended this act of twucking can also be called "Flesh Guitar" as it looks like the person being lifted is a guitar.
Ryan:- Sorry about all the noise from my room last night, my girl and I were having some fun.
Caolan:- That was some noise you guys were making, playing the flesh guitar?
Ryan:- Nah, just some normal twucking.