See the results in results.txt here are a few: paracystitis pansinuitis pyrolysis phlebometritis paramastitis parosteitis pathopsychosis phosis parahypnosis pylorostenosis paralepsis pneumarthrosis paraproctitis patois pneumocentesis polyserositis pneumonophthisis paraphysis paraphronesis pseudankylosis proglottis polyposis perisinusitis pentapolis parapraxis pneumatosis peribronchitis perididymis pteris prepubis pollenosis pyopneumocholecystitis palaeornis prorrhesis patriofelis phalacrosis perisinuitis pericardiolysis panidrosis portugais porencephalitis psychognosis pyoptysis phronesis perigenesis prosopantritis perihepatitis pyonephrosis presbycousis phlebostenosis pythogenesis pyelocystitis pyrosis protasis polyphylesis pseudoarthrosis persis prothesis paridrosis pneumomycosis prenaris procatalepsis piptomeris parenchymatitis periarteritis
python script that solved the question on reddit.com/antijokes asking: "what starts with p and ends with is?"
Thanks to https://github.com/dwyl/english-words for their great list of english words