Sentence:  the anaconda reaches a length of at least 37 feet , the reticulate python 33 , the African rock python 25 , the amethystine python at least 22 , the Indian python 20 , and the <WSD>boa</WSD> constrictor 18 - 1 2 . 
Meaning of the word marked with <WSD> tags:  very large boa of tropical America and West Indies