When my cat is doing something he knows is bad, such as trying to chew on flowers, I will snap my fingers and say his name and he will chatter back at me. He will stop doing it, but I'm just curious as to why he chatters at me.
You don't really describe the vocalization, so let me know if I am way off the mark.
Cat "chattering" is a typical vocalization response when a cat sees a bird or a rodent outside a window. It is typically thought that they chatter in a state of high anticipation or possibly frustration in response to the surge of adrenaline.
A recent study suggeststhat cats may actually be trying to imitate various sounds they hear as a hunting technique.
YouTube is full of videos of cats coincidentally or intentionally trying to make human-like sounds. Who knows; maybe he's trying to tell you to stop beotching at him so much <grin>.
I've heard a claim that the rapid jaw motion in the "chitter" is actually a specialized bite, which works the teeth between the prey's vertebre to sever the spinal column. I have no credible citation, alas, but I've alwsys interpreted it as "I'd bite that, but I can't." Maybe in this case it's "I'd bite that but I'd get my furry butt whipped" -- another form of feline cursing to go with hiss, yowl, and the time my siamese pointedly made burying motions in my direction.