Bold, daring, or unflappable; someone who remains calm and composed in risky or difficult situations.
彼女は肝が太いから、大勢の前でも臆せずに話せる。
She is fearless and can speak in front of large crowds without hesitation.
あんな危険な状況で冷静に行動するなんて、本当に肝が太い人だ。
Acting calmly in such a dangerous situation — truly a person with guts.
面接で厳しい質問にも落ち着いて答え、彼は肝が太いと評価された。
He answered tough interview questions calmly and was regarded as having a lot of nerve.