gakoauauotamateapokaiwhenuakitanatahu is the Māori name for a hill, 305 metres high, close to Porangahau, south of Waipukurau in southern Hawke's Bay, New Zealand.

I IMed a buddy and he replied with 28 letter Antidisestablishmentarianism. So I looked it up to remind me of the definition.

Which led me to 45 letter
Pneumonoultramicroscopicsilicovolcanoconiosis
http://en.wikipedia.org/wiki/Pneumonoultramicroscopicsilicovolcanoconiosis


Which led me to 85 letter
Taumatawhakatangihangakoauauotamateapokaiwhenuakitanatahu
http://en.wikipedia.org/wiki/Taumatawhakatangihangakoauauotamateapokaiwhenuakitanatahu