Yep, this is an acronym.
It's just that I am tempted to use this acronym so often that I have (now) eventually got to feel that this acronym deserves, from me, a public explanation, so that in the future I can just refer to this explanation, instead of explaining it all again.
It's mostly about/used when I need to write/type instead of speak.
Although I am a poor speaker, for me, there are still huge advantages of speaking, compared to writing/typing, one of which is how important is a certain word/sentence/idea, compared to other/neighbouring words/sentences/ideas. If I speak faster and rush through something, it must be rather unimportant; conversely, if the speed was somewhat suddenly decreased, then the idea had better be one that is being emphasized.
However, a written sentence, especially without formatting(e.g. like this), could be read in different ways, each emphasizing different components of the idea/sentence. Together with the way in which written content is open/prone/supposed/intended/designed/written to be read multiple times, the meaning which is supposed to be delivered would possibly (or even likely) be different from, or cannot accurately reflect, what the original idea was, or was like.
Most of the time when I actually write things down, I intend to mean exactly what I write. I make effort in making it possible to link most of my words to some Wikipedia page to nail down which meaning (of the word) am I intending. However sometimes, I just can't manage to nail down which specific meaning it is. Sometimes I don't even know of the choices of rigorous meanings from which to choose!
Therefore, it would be handy if I had a tool to mean something like "Hey, you see, I know people use this word, right? - But I kind of don't really know what they mean when they say it (?). I don't have in mind a specific way in which I would like you to interpret this word/saying, so just understand it however you feel like to.".
Well, "WTM" does exactly that.
In other words, I'm (consciously/deliberately) not focusing on this word for the point/purpose of this sentence. Please don't take this word too seriously or pay too much attention to it.