What does "double dribble" mean in basketball?

Touching the ball with both hands, letting the ball come to rest during possession or touching the ball more than once before it comes in contact with the floor while dribbling results in a "double dribble" violation. The penalty is loss of possession by the violating team.

Per NBA rules, possession is awarded to the opposite team at the sideline nearest the violation but no closer to the baseline than the extended free throw line. Such infractions are "whistled" by an official, who signifies the call by placing her arms and fingers straight with palms facing the ground while moving her arms up and down simultaneously.