This is the 3368th most frequent Japanese word.
本音
True feelings; real intentions.
Here, '本音' refers to someone's genuine or real feelings or thoughts, beyond what is externally expressed.
彼女の本音を聞いたら驚いた。
I was surprised when I heard her true feelings.
In this sentence, '本音' is used to signify the speaker's sincere expression of their true feelings or personal standpoint.
本音を言えば、このプロジェクトには興味がない。
To tell the truth, I am not interested in this project.
Here, '本音' relates to the concept of not openly revealing one's true emotions or intentions.