Mammoth Uncensored Word List:
24 - 15 letter words starting with fe

featherbeddings featherstitched featherstitches featurelessness federalisations federalizations feebleheartedly feloniousnesses femtobecquerels femtochemically fencelessnesses ferociousnesses ferricytochrome ferrimagnetisms ferrocalcinosis ferrocytochrome ferromagnetisms ferromanganeses ferromolybdenum ferroprussiates fertilizability fertilizational fetishistically feuilletonistic