Thing Not To Be Today: nonplussed.

 Here in Britain, I was completely nonplussed to discover the  widely-understood American meaning of the word nonplussed.

I'd make some suggestion about how we can resolve this ridiculous situation.

But I'm completely nonplussed.

Thing Not To Be Today: nonplussed. In Britain to be nonplussed is to be so taken aback (that is, surprised and confounded) by a situation that one can't act, or even speak.

The word comes from the Latin nōn plūs, which means no further, the idea being that nothing more can be said or done.

In the USA I understand that nonplussed is often used to mean completely unmoved, or poised in the face of a difficult situation. 

Merriam Webster still marks this meaning as mistaken, but we seem to have got to the stage where the poor word is more or less unusable.