noun
liver and gall bladder; one's inner being
Literally refers to the liver and gall bladder, but commonly used in set phrases like 肝胆相照らす (to be open-hearted with each other) to mean one's deepest feelings or true self.
肝胆相照らす仲だ。
We are close enough to bare our hearts to each other.
彼の言葉が私の肝胆を揺さぶった。
His words stirred my innermost feelings.