A BALL is a pitch which does not enter the strike zone in flight and is not struck at
by the batter.
Rule 2.00 (Ball) Comment: If the pitch touches the ground and bounces through the strike zone it is a “ball.” If such a pitch touches the batter, he shall be awarded first base. If the batter swings at such a pitch after two strikes, the ball cannot be caught, for the purposes of Rule 6.05 (c) and 6.09 (b). If the batter hits such a pitch, the ensuing action shall be the same as if he hit the ball in flight.
A pitched ball that bounces can be hit or fouled. In this video Vladimir Guerrero hits a bounced pitch for a base hit.