Longest word in the dictionary

It has 45 letters!

Pronounciation: 

[noo-muh-noh-uhl-truh-mahy-kruh-skop-ik-sil-i-koh-vol-key-noh-koh-nee-oh-sis, nyoo-] 

What does it mean? An obscure term ostensibly referring to a lung diseasecaused by silica dust, sometimes cited as one of the longestwords in the English language. 

Source: http://www.dictionary.com/browse/pneumonoultramicroscopicsilicovolcanoconiosis