Powerful crashing waves that "break" into foam on or near shore. The roar of breakers along the west coast of Vancouver Island often caused panic for a ships' crew because it meant that they had come to close to the rocky shore and were in danger of wrecking. Because of the awesome and unpredictable power of breakers, they are often almost impossible to swim through.
A wave that approaches shallow water, causing the wave height to exceed the depth of the water it is in, in effect tripping it. The wave changes from a smooth surge in the water to a cresting wave with water tumbling down the front of it.