Strong Spirit
Backbone
noun
A spirit of approximation is the approximation of spirit. My approximation of your spirit? I think you have a strong spirit. I think you have backbone.
気概 is a formal word mostly used in writing. It refers to someone's strong spirit in the face of challenges. It conveys a sense of courage and moral strength, often associated with pride and resilience in difficult situations.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
その教師は、教室で見て見ぬふりをされている問題に取り組む気概がなかった。
The teacher didn’t have the guts to deal with the problems in the classroom.