Mammoth Uncensored Word List:
23 - 13 letter words starting with wo

woebegoneness wolfishnesses wollastonites womanlinesses wonderberries wonderfulness wondermongers woodburytypes woodchoppings woodcraftsman woodcraftsmen woodsheddings woolgatherers woolgathering woollystemmed wordishnesses wordmongering wordprocessor workabilities worldlinesses worrisomeness worshippingly worthlessness