noun, な adjective
Something that's not calm is in a state of unrest. When things are unsettled, it's disquieting for people.
不穏 is generally used to describe the unsettling mood or atmosphere of a situation, highlighting tension and unease rather than describing something physical.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
Tonight’s crescent moon looks a little disquieting to me.