Mammoth Uncensored Word List:
30 - 20 letter words starting with c

chemicophysiological chemicophysiologists chemoautotrophically chemostratigraphists chemotherapeutically chemotherapeuticness chlorofluoromethanes cholecystnephrostomy chronostratigraphers chronostratigraphics chronostratigraphist compartmentalisation compartmentalization comprehensiblenesses contradistinguishing conventionalizations counterconditionings counterdemonstrating counterdemonstration counterdemonstrators counterintelligences counterintuitiveness countermobilizations counterrevolutionary countersurveillances countertransferences crystallographically crystalloluminescent cyclostratigraphists cytodifferentiations