Sentence:  The most infamous of all was launched by the explosion of the island of Krakatoa in 1883 ; it raced across the Pacific at 300 miles an hour , devastated the coasts of Java and Sumatra with <WSD>waves</WSD> 100 to 130 feet high , and pounded the shore as far away as San Francisco . 
Meaning of the word marked with <WSD> tags:  one of a series of ridges that moves across the surface of a liquid (especially across a large body of water)