Synonyms for Horse Chestnut (same or very similar meaning)
WordNet sense 1 (the inedible nutlike seed of the horse chestnut):
buckeye, conkerWordNet sense 2 (tree having palmate leaves and large clusters of white to red flowers followed by brown shiny inedible seeds):
Aesculus hippocastanumFrom the ODE community, based on WordNetadd/edit