A lover of words; particularly long words. These people don't merely love these words, they lust these words, they fantasize about them, they fucking ADORE THEM!
The lives of Sesquipedalians are words, they live, breathe and eat words. Literally. Extreme Sesquipedalianism (or ES) is a condition whereby a patient reports excessive masturbation and intrusive sexual thoughts about words. Treatment is sparse.
Nick: Hey, I redecorated the bedroom with Predominantly last night.
Warren: You're such a sesquipedalian! I love Paradoxically so much I think i could cry.