[count], 1 a : a mass of air that moves very quickly and forcefully, She opened the door and felt a cold blast. a blast of wind, b : a mass of water, gas, heat, etc. that moves very quickly and forcefully through the air, He was hit by a blast of water from the hose. a blast of heat, 2 : the loud sound made by a horn or a whistle, The driver gave a long blast on his horn. the blast of the factory whistle, a bugle blast, 3 : a powerful explosion, The bomb blast killed eight people. a shotgun blast, 4 : a sudden powerful force, She got a blast of reality when she returned to school in the fall. a blast of criticism, 5 informal : a very enjoyable and exciting experience, I had a blast at your party. The wedding was a blast.