Sentence:  Mantle , the bull-necked blond switch-hitter , had one sensational triple-crown season , 1959 , when he batted .365 and also led the <WSD>American</WSD> League in home runs , 52 , and RBIs , 130 . 
Meaning of the word marked with <WSD> tags:  any number of entities (members) considered as a unit