The Collaborative International Dictionary
Sesquipedalianism
Sesquipedalianism \Ses`qui*pe*da"li*an*ism\, Sesquipedalism \Ses*quip"e*dal*ism\, n. Sesquipedality.
Wiktionary
sesquipedalianism
n. (context uncountable English) The practice of using long, sometimes obscure, words in speech or writing.