I only think of processing in the clinical sense. Bear in mind, I remember all of my trauma.
So, if I started with a bunch of memories that were a big knotted tangled ball of yarn, every time my therapist and I work through a moment in my memory - that is equivalent to getting one tangle to be untangled. And then, we move on to the next knotty part.
Most of it is done in a linear fashion (chronological time), but sometimes there are knots within knots (memories that draw on or are informed by other memories), and then we work on untangling all those snarls.
Eventually the mass of tangled yarn will be able to be wound back into a fairly smooth ball; it's not gone, but it's manageable, and I can put it in the bin with the other balls of yarn (other parts of my life and experiences) and not worry that it's going to snag another ball and make an even bigger mess.
By "work through", in my case I mean EFT. But Exposure therapy, EMDR, brainspotting, somatic therapy, cranio-sacral, IFS, CBT - basically, using any therapeutic modality where you are untangling knots in a systemic way - that is what I'd call processing.
Which is why I don't believe anyone can do it effectively entirely on their own, at least not at first. I lived for a long time thinking that I had "processed" what happened to me. Really, all I did was wind all the loose knots into tighter knots in the hope that I could just bundle the mess that was there, if that makes any sense.
I personally also believe that you can't just use any old therapy style to process trauma. There are ones that have clinical data backing them up and others that don't.
(I actually do a type that doesn't have a ton of data - but I have my own theories about why it works, and it's related to the other modalities in many ways. Anyway, for now, I have enough evidence within myself to know its effective. When it stops being so, I'll change working methods).