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 waves 100 to 130 <WSD>feet</WSD> high , and pounded the shore as far away as San Francisco . 
Meaning of the word marked with <WSD> tags:  a linear unit of length equal to 12 inches or a third of a yard