progressive disturbance propagated through a fluid such as water or air as the result of displacement by the foremost point of an object moving through it at a speed greater than the speed of a wave moving across the water. Viewed from above, the crest of the bow wave of a moving ship is V-shaped; the angle of the V is determined by the relative speeds of the ship and of the propagation of waves in the water.In three-dimensional space—for example, when describing the wave produced by a plane flying at supersonic speed (supersonic flight)—the bow wave is conical in shape. In this case an observer on the ground experiences a sonic boom when the bow wave passes. See also wave motion.