What is "pneumonoultramicroscopicsilicovolcanoconiosis"

1962, "A facetious word alleged to mean 'a lung disease caused by the inhalation of very fine silica dust' but occurring chiefly as an instance of a very long word" [OED]. Said in an early reference to have been invented by seventh grade students in Norfolk, Virginia.

n. (label en nonce) A factitious disease of the lungs, allegedly caused by inhaling microscopic silicate particle originating from eruption of a volcano.

Pneumonoultramicroscopicsilicovolcanoconiosis is an English word that refers to a lung disease that is otherwise known as silicosis. It is the longest word in the English language published in a dictionary, the Oxford English Dictionary.

According to the Oxford English Dictionary, it is "an artificial long word said to mean a lung disease caused by inhaling very fine ash and sand dust."

Silicosis is a form of occupational lung disease caused by inhalation of crystalline silica dust, and is marked by inflammation and scarring in the form of nodular lesions in the upper lobes of the lungs. It is a type of pneumoconiosis.