Mammoth Uncensored Word List:
41 words ending with ns, 19 letters long

bourgeoisifications chlorofluorocarbons counterinstitutions counterreformations counterretaliations disproportionations electrocoagulations electrodesiccations establishmentarians evapotranspirations hyperconcentrations hypersensitizations iatromathematicians intercommunications microencapsulations noventrigintillions overcapitalizations overcentralizations overclassifications overgeneralizations overidentifications overinterpretations overrepresentations oversimplifications overspecializations ovolactovegetarians photodecompositions photosensitizations phytohemagglutinins polyesterifications postmultiplications proletarianisations proletarianizations sentimentalizations septemvigintillions supersensitisations supersensitizations territorializations transmogrifications transubstantiations trigintacentillions