Mammoth Uncensored Word List:
27 words ending with fs, 11 letters long

breadstuffs broomstaffs bumbailiffs chiffchaffs childproofs cloverleafs crashproofs demireliefs flameproofs frostproofs greenstuffs hippogriffs lightproofs mallowpuffs mutessarifs powderpuffs quakeproofs shandygaffs shockproofs soundproofs stainproofs stormproofs stouthriefs stroganoffs thornproofs undercliffs waterproofs