Mammoth Uncensored Word List:
15 words that are 19 letters long beginning with r in the mammoth uncensored word list.

radioallergosorbent radiopasteurization radiopharmaceutical reconceptualisation reconceptualization reindustrialization reinstitutionalized reinstitutionalizes reprehensiblenesses representationalism representationalist reticuloendothelial retroreflectometers revolutionarinesses rhinolaryngologists