Feeling Bad, Feeling Terrible, Unpleasant, Gross
い adjective
きもちわるい
二日よいで、頭はガンガンするし、めっちゃ気持ち悪いし、最悪だよ。
I'm hungover, I have a bad headache, and I feel terrible. This is awful.
コウイチは気持ち悪いネコなで声で、ビエトをよんだ。
Koichi called out to Viet with his sickly sweet voice.
ちょっと、そんな風に腕を曲げるのやめてくれない？めちゃくちゃ気持ち悪いんだけど。
Stop bending your arms like that. It’s seriously weirding me out.
The 気持ち (feeling) is bad. So, you can imagine how you feel isn't good, it's a bad feeling. You're feeling terrible, in fact.
The readings come from the words 気持ち and 悪い. Hopefully you've seen both and can combine them together to know the reading automatically. No bad feelings with this word, right?