nacreous

[mkenuk]

  a word should be classed as rare if a lot of people don't know it.

.

In that case, Alan, would you agree that nacreous - classed as common in the cavernous game - should be made rare?

It was played by 34 from 349 players (slightly under 10%).

I'm not even sure how it should be pronounced. 'nakerous'? ''nakrious'?
Needless to say, I can't remember ever seeing or hearing it before.

MK   

[TRex]

I agree.

[Alan W]

Well, I've left this a good long time to allow someone to pipe up that as far as they're concerned nacreous is a normal everyday word, and they'd be sorry to see the puzzle being dumbed down by classing it as a rare word. Not really - I've left it till now because I haven't got around to replying.

It is a word that appears quite rarely in general publications. Perhaps surprisingly, a big percentage of the examples in the News on the Web corpus were from the Daily Mail - from one article in February 2016, Devastatingly beautiful: Rare nacreous clouds seen painting the skies across the UK - but despite their splendour, the formations can cause holes in the ozone layer.

Nacreous will be a rare word from now on.

[birdy]

Another one I know, mostly in the context of pearls, though the examples I just looked up had more to do with clouds.  But I would agree that it isn't common.