Meaning
(1) kategoros, that is, a prosecutor, or plaintiff in a lawsuit, or one who speaks in a derogatory way of another (Act 23:30, Act 23:35, Act 25:16, Act 25:18, Rev 12:10);
(2) diabolos, meaning adversary or enemy. This word is rendered "accuser" in the King James Version and "slanderer" in the Revised Version (British and American) and the American Standard Revised Version (2Ti 3:3, Tit 2:3). According to the rabbinic teaching Satan, or the devil, was regarded as hostile to God and man, and that it was a part of his work to accuse the latter of disloyalty and sin before the tribunal of the former (see Job 1:6 ff; Zec 3:1 f; Re 12:10).
W. W. Davies