Living with an English teacher.

One of the pleasures of (semi) retirement is that breakfast is seldom fraught and time can be spent in reading, sharing crosswords, and generally entering the day on an even keel. At breakfast recently I was dragged from contemplation of my Futoshiki by a question.

What is the opposite of decorous?

Scruffy.

I replied hoping to slip back unnoticed into the logical simplicity of more than or less than of my puzzle. Fat chance, a gentle clearing of the throat produced a hesitant

Indecorus?
on my part.

Further interrogation and consultation of the written authorities produced a consensus that the word being sought for the solution of a crossword clue was the noun indecorum.

I've certainly never used it and given the vagaries of memory at my age have little recollection of it being used in my presence. I would have horse whipped any bounder who had done so sir!