Longman Dictionary of Contemporary English - flatten

~ v 1 also flatten out to make something flat or flatter or to become flat or flatter  (Noah flattened the cardboard boxes before throwing them away. | The land flattened out as we neared the coast.) 2 to destroy a building or town by knocking it down, bombing it etc  (Dresden was flattened in the war.) 3 flatten yourself against to press your body against something  (I flattened myself against the wall.) 4 informal to defeat someone completely and easily in a game, argument etc  (We flattened them 6-0.) 5 informal to hit someone very hard