A blast is an explosion, or a sudden sharp noise. When you blast someone, you either shoot them, or hit them with a verbal explosion––a tirade of criticism.
Your teacher might blast your class for being rowdy; she’ll go on and on about how you are acting like first graders. On the Fourth of July, you might hear a different kind of blast — first your neighbors' bottle rockets, then the explosion of fireworks sponsored by your town. It's very exciting to watch a rocket launch into space––little kids love to play at the game, chanting, "5...4...3...2...1...blast off!