sesquipedalianism

is likely misspelled.

has no English definition.

As a noun sesquipedalianism

is the practice of using long, sometimes obscure, words in speech or writing.

As nouns the difference between sesquipedalianism and sesquipedalianist

is that sesquipedalianism is (uncountable) the practice of using long, sometimes obscure, words in speech or writing while sesquipedalianist is a person who tends to use sesquipedalian words.