Answer :
Basically it means when something is moving in a line and is rotating in a larger system at the same time it appears to move. If you look it up online you can easily find a picture or two that should explain it pretty well.
The Coriolis effect is an effect whereby a mass moving in a rotating system experiences a force (the Coriolis force ) acting perpendicular to the direction of motion and to the axis of rotation. On the earth, the effect tends to deflect moving objects to the right in the northern hemisphere and to the left in the southern and is important in the formation of cyclonic weather systems.
Hope This Helps ^_^