The Greek verb diakatelenchomai means to refute or convince thoroughly and conclusively — to defeat an opponent's arguments completely. It appears only once in the New Testament, in Acts 18:28, describing Apollos who 'powerfully refuted the Jews in public, demonstrating from the Scriptures that Jesus was the Messiah.'
The single appearance of diakatelenchomai in Acts 18 highlights Apollos as one of the most gifted apologists in early Christianity. Having received better instruction from Priscilla and Aquila, Apollos returned to public debate with greater power — not relying on rhetoric alone but demonstrating from the Scriptures. This is the model of Christian apologetics: thorough Scriptural knowledge deployed in public, leading not just to intellectual checkmate but to conviction. The word suggests that Apollos didn't just win arguments — he demolished the opposition's case entirely. This gift of powerful apologetic reasoning, rooted in Scripture, is a spiritual gift for the church's mission.