The Greek verb apotolmao means to be very bold, to dare completely, or to speak with great audacity. The prefix apo- intensifies tolmao (to dare/be bold), making this word mean an extreme boldness — going all out in daring to speak. It appears once in the New Testament in Paul's defense of his apostolic boldness.
Apotolmao appears in Romans 10:20, where Paul quotes Isaiah 65:1 with the introduction: 'And Isaiah boldly [apotolma] says...' The 'boldness' refers to Isaiah's daring proclamation that God would be found by those who didn't seek Him — a reference to the Gentiles finding salvation. Paul highlights Isaiah's courage in speaking a word that would be scandalous to Jewish ears. Theologically, the word models prophetic boldness — speaking God's truth even when it is counterintuitive, offensive, or dangerous. This is the boldness that the Holy Spirit gives to Christ's witnesses.