Mammoth Uncensored Word List:
14 - 19 letter words starting with se

semiconsciousnesses sentimentalizations septemvigintillions septendecilliardths septentrigintillion septingentillionths septuagintilliardth septuagintillionths sesquipedaliophobes sesquipedaliophobia sesquipedaliophobic sesquipedalophobics sestrigintillionths sexagintacentillion