What does pneumonoultramicroscopicsilico-volcanoconiosis mean?
(The entire word will not display in either the question box or answer unless a hyphen is used.)
It is a lung disease, similar to 'black lung' usually acquired by miners. It is caused by extremely microscopic silica getting into the lungs. Literally the word means: 'a lung disease caused by the inhalation of very fine silica dust usually found in volcanoes'.
The term (more simply called pneumoconiosis, related to silicosis) is
pneumonoultramicroscopicsilico-volcanoconiosis (no hyphen)
and was created in 1935 to be 'the world's longest English word".