Mammoth Uncensored Word List:
21 words ending with ds, 15 letters long

allotetraploids apprenticehoods archpriesthoods autotetraploids brachypinakoids cercopithecoids containerboards corticosteroids glucocorticoids lepidodendroids micrometeoroids nonvolatilizeds octodecilliards parallelepipeds parallelopipeds philanthropoids quindecilliards trecentilliards trigintilliards trypanosomatids vespertilionids