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 <WSD>miles</WSD> an hour , devastated the coasts of Java and Sumatra with waves 100 to 130 feet high , and pounded the shore as far away as San Francisco . 
Meaning of the word marked with <WSD> tags:  a unit of length equal to 1,760 yards or 5,280 feet; exactly 1609.344 meters