any of several waterlilies; esp., a North American species (Nuphar advena) with thick roots, heart-shaped leaves, and yellow flowers
See spatterdock in American Heritage Dictionary 4
(spătˈər-dŏkˌ)
noun
An aquatic plant (Nuphar advena) of eastern Mexico and the eastern and central United States, having emergent broad leaves and globe-shaped yellow flowers.