What is the longest word in the dictionary?

[HHLLsaruh]

the longest word in the dictionary is pneumono­ultra­micro­scopic­silico­volcano­coniosis,
pronounced
new-mon-uh-ultra-microw-sco-pic-silico-volcan-i-cone-ee-oh-sis

my little brother and I would have competitions to see who could spell the longest word, and he won with this one
=]  

[[ToXiC][ToOtHpAsTe]]

I have no clue. I'm not exactly sure how to spell it but I know a chemical for rocket fuel, my granpa taught me how to pronounce it when I was three. x3

Uncymetrical Dymethal Hydrozine (Though there are space, there are words with spaces in the dictionary, :3 )  

[Mira_Russ]

I've always been told it's pnuemoultramicroscopicsilicovolcanoconiosis--but it is a type of disease, so I don't know if that counts or not.