This is dictionary.com’s word of the day today. It sounds disturbing, but it means “twilight, dusk”. Hardly as ominous as it sounds. The word comes to us from the Latin, they say, around the year 1400.
It just struck me as odd, and I thought you might be entertained by it. Hard to imagine using it in a sentence, though dictionary.com does give examples. Try it on your friends tonight!