Mammoth Uncensored Word List:
29 - 16 letter words starting with pe

pentanonagesimal pentasexagesimal pentoctogesimals perceptibilities perceptivenesses percussivenesses peremptorinesses perfectibilities perfectivenesses perfidiousnesses perfluorocarbons performabilities pericardiotomies perineorrhaphies periodontologies periphrastically permissibilities permissivenesses perniciousnesses perpendicularity personablenesses personalizations personifications persuasivenesses persymmetrically pertinaciousness petrochemistries petrographically petrosomatoglyph