expression, adverb
without reserve; frankly; openly
Used when speaking one's mind honestly and without holding back. Often appears in formal or written contexts.
腹蔵なく意見を述べてください。
Please state your opinion frankly.
彼は腹蔵なく自分の考えを話した。
He spoke his thoughts without reserve.
From 腹蔵 (ふくぞう, 'keeping in one's heart') + なく ('without'). The exact historical derivation is uncertain, but the expression is conventionally associated with the idea of not hiding one's true thoughts.