The Greek keleusma (from keleuō, to command) is the shout of command given by a commander to his troops, a coxswain to his rowers, or a hunter to his hounds. It appears only once in the New Testament — 1 Thessalonians 4:16: 'For the Lord himself will descend from heaven with a keleusma, with the voice of an archangel and with the trumpet of God.' It is the authoritative, commanding shout that initiates the resurrection of the dead.
The keleusma of 1 Thessalonians 4:16 is the most dramatic single word in the New Testament's eschatological vocabulary. When Christ descends, his shout (keleusma) is the command that ends death's dominion — the commanding officer calling his soldiers up from the dead. This is the same voice that called Lazarus from the tomb (John 11:43), the same voice that created the universe (John 1:3). The resurrection is not a slow awakening but a military-style snap-to-attention at the voice of the commanding Lord.