Mammoth Uncensored Word List:
60 - 14 letter words starting with so

sobersidedness sociablenesses socialisations socializations socialsecurity sociobiologies sociobiologist sociolinguists sociologically sociopolitical socioreligious sociosexuality softheadedness solecistically solemnisations solemnizations solicitorships solicitousness solidification solifidianisms solitarinesses solitudinarian solubilisation solubilization solvablenesses solvatochromic somaesthesises somatotrophins somnambulances somnambulating somnambulation somnambulators somnambulistic somniloquences somniloquising somniloquizing sonorousnesses soothingnesses sophisticating sophistication sophisticators soporiferously sorbitisations sorbitizations soreheadedness sorrowlessness soteriological souldestroying soullessnesses soundproofings southeasterner southeastwards southernnesses southwesterner southwestwards sovereigntists sovietisations sovietizations sovietological sovietologists