Semantics will confuse people all the time. The actual vaping definition of 'rebuildable' does mean exactly as posted here - an atomizer you can strip right down to the coils and re-wick and re-coil. The term is also used by people when talking about just replacing the atomizer portion (with new wicks and coils already in place) instead of throwing the whole delivery device (like a clearomizer) away and buying a new one.
We probably should use 'replaceable' when talking about replacing the atomizer in the deliver device vs rebuildable for those that do 'rebuild it from the bottom up, so to speak.
Which way you go is your choice. I would love to be one of those hands on, good tool user and be able to rebuild an atomizer if for no other reason then once I had made the investment in the few needed tools and supplies I would be saving lots of money and could pat myself on the back. I did try one time, with a bit of wick and coil and lots of tutoring from a friend but quickly found out that neither my eyesight or hand-eye coordination was up to the job. That's not to say its hard to do but in my circumstances I pretty much ended up with the coil around my finer and the wick in my ears. It does cost only a few cents to rebuild the atomizer - but remember that you have an initial investment of some dollars depending if you already have the right tools for the job and your wicking and coil. At a few cents a rebuild its a while before you recoup your investment and see your savings.
However, taking apart my clearomizers, tanks etc and cleaning them and, as necessary, replacing the atomizer saves me a great deal of money too. Its also very easy to do because someone else did the coil, wick and testing part. Depending on the atomizer I can replace mine for anywhere from less then a dollar to only a few dollars. This is a great deal less then buying a new one once cleaning alone just does not do the job.
People also mean by 'rebuildable' or 'replaceable' that you an strip down to clean it well and keep it going even if you never get into to atomizer replacement in you delivery system.
There are also 'disposables' which can be re-used (refilled) a bunch of times and even cleaned (but as they do come apart not as easily or well) and when they start tasting bad - you just toss them. Even though they might have a price tag of less then a rebuildable or replaceable atomizer system they end up costing the most because the length of time you can use them is limited. For example, I can pay $8 for a disposable CE4 clearomizer and even with washing it out and giving it a dry burn the longest I can make it last is 2-3 weeks and then its into the trash. For $10 dollars I can get a 'rebuildable' one which I can take apart, wash and when the atomizer gets really glunked up so that washing and a dry burn is not the answer I replace the atomizer which cost me less then a dollar each and its like brand new. (And if you rebuilt the atomizer it a delivery system that offers those parts it would only new pennies). I have 5 clearomizers I have had now for the better part of a year that I just replace the atomizer when necessary and save myself a bit over $9 each time.
If you go to You Tube you can watch many video's on rebuilding atomizers and replacing them which will help give you an idea of what people are talking about.