Noun
こうきしん
子どもの頃、私は好奇心旺盛でした。
When I was a child I was full of curiosity.
You like it because it gives you an odd feeling in your heart. You don't quite know what it is you like, but that's because it's curiosity that you have.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.