1. Nonsense vs. a nonsense. 

'Nonsense', in the first instance, pertains to the meaning of a phrase or a sentence; either it has sense (it makes sense), or it's nonsense (it makes no sense).  Either it is semantically, lexicographically and grammatically in order, or something is semantically, lexicographically or grammatically very wrong; it fails to express a coherent thought. 

'Nonsense' is an adjective, but one occasionally finds the use of the term as a noun, ie 'a nonsense' (I've come across this use even by Frank Ramsey!). 'A nonsense' implies that one can count nonsenses, which one might well resist.  Is it connected with the senses? I see an image of a blind man groping - that he can't find his way; that to say 'It's a nonsense' is roughly to say 'I see nothing with it', or 'One cannot use it to see anything'.  

There is also a use where what has been said succeeds in expressing a thought, but where the thought is egregiously false. Perhaps this use is connected with the first, in that if we have an example of nonsense (of this second variety), then no coherent case can be made for it. 

2. Paradoxes of Relativism. 

The central paradox being that it is self-defeating to proclaim that all is relative. Is it relative to say that all is relative? If it is not, then not all is relative; but if one proclaims that it is, one adopts a point of view from which it is not (there is one thing that one can say that is not relative, namely that all is relative). It is not actually a paradox, but it seems necessarily false.     

Frequently the 'paradox' is met with in lower grades, ones that are not in themselves self-contradictory.  Once in while it emerges with special poignancy. Boris Johnson recently announced a relaxation of the Covid-era rule that social isolation is mandatory if you have a positive test: It will no longer be enforced.

An interviewer:

What do you think of Boris's announcement? 

Interviewee: 

Well, for me, I'd say you should isolate. 

Does he mean 'I should isolate'? No. Something stronger.  Does he mean 'Everyone should isolate'? He would say he didn't mean that, either. The interviewee is struggling.

What is going on? Maybe people do believe that matters of morality are not, at all events, relative, but that it's uncool to say it.  It's uncool to play the preacher-man; one doesn't like the responsibility that the institution of morality demands. 

I connect the phenomenon with the newish habit, in writing, of ending certain declarative sentences with a question mark. People are hesitant to make assertions, to use outright declarative sentences, on certain topics. 

3. Possible Miswordings that might take off 

[Cancelled! I was WRONG! I'll leave up as penance]

 'Defenestration'

The word means removal of windows, especially if the removal is violent (notorious with the Protestant thugs of the 16th century). Dylan Byers obtained a recording of a CNN staff meeting with WarnerMedia CEO Jason Kilar, to explain the network’s sudden dismissal of Jeff Zucker:

It did not go well. The meeting, which I obtained a recording of last night, highlights the profound sense of loyalty that CNN’s on-air talent have toward their longtime leader, despite his violation of company policy, and the anger they feel regarding the circumstances of his sudden defenestration.

No comment. 

b. 'It's incredulous!' 

Though not often but I venture increasingly, the word is sometimes used for incredible, for a phenomenon (not a person, as is required by 'incredulous'). I've also heard of 'contemptuous' being said for 'contemptible'.  An example from an advertisement for a kitchen utensil: 

The Original Milk Frother has a $17 price tag, which isn’t bad at all considering it makes the most delicious foam and is far from Starbs’ incredulous prices for a simple cup of joe.

This is an attempt to compensate for being lexicographically ill-informed by making up new uses of words, that, though only to their fellow linguistic deficients at most, will seem learned, rather than as further confirmation of their deficiency.