Kērussō (κηρύσσω) means to proclaim as a herald, to make public announcement, to preach. The noun kērux (G2783) is a herald — an official messenger who announces on behalf of a king or authority. Kērussō appears about 61 times in the NT and, along with euangelizō (G2097, to evangelize), is the primary word for the church's proclamation of the gospel.
The herald doesn't offer opinions or facilitate dialogue — he delivers his king's message with full authority, expecting it to be received. This is the posture of NT proclamation.
Kērussō is the verb of the Kingdom's invasion. Jesus began his ministry "proclaiming" the gospel of the Kingdom (Matt. 4:17, 23). He sent out the twelve to "proclaim" (Mark 3:14). After his resurrection, the church received the commission to "proclaim" repentance and forgiveness "to all nations" (Luke 24:47).
Paul describes his entire apostolic calling through this word: "For Christ did not send me to baptize but to preach [kērussō] the gospel" (1 Cor. 1:17). The content of the proclamation — the kērygma — is Christ crucified and raised (1 Cor. 15:1-11). Paul warns against another gospel (Gal. 1:8-9) and urges Timothy to "preach [kērussō] the word" in season and out (2 Tim. 4:2). The church's fundamental calling is not merely to offer programs or meet needs, but to herald the King's news.