Short for counterclockwise, CCW is the rotation or movement of an object that's the opposite direction of the hands movement on a clock. Beginning from the top, a circular rotation moves to the left, and from the bottom rotation moves to the right. For instance, when removing or loosening a screw, you would rotate the screwdriver to the left. The image shows both an example illustration of the both the clockwise and counterclockwise directions.
An easy way to remember how to adjust screws and knobs is with the popular saying "righty tighty lefty loosey."