Mammoth Uncensored Word List:
33 words ending with p, 14 letters long

accountantship ambassadorship anticensorship apprenticeship archpriestship bipartisanship cardmembership catechumenship chancellorship cochairmanship codirectorship commandantship commissaryship consultantship controllership councillorship counsellorship goodfellowship headmastership instructorship legislatorship licentiateship lieutenantship magistrateship noncitizenship postmastership procuratorship progenitorship prolocutorship proprietorship stadholdership supercargoship supervisorship