From Longman Dictionary of Contemporary Englishhorse chestnutˌhorse ˈchestnut / $ ˈ. ˌ../ noun [countable] 1 HBPa large tree that produces shiny brown nuts and has white or pink flowers2 HBPa nut from this tree SYN conker
Examples from the Corpus
horse chestnut• Some leaves are especially toxic: those of evergreens like holly and laurel, as well as horse chestnut and willows.• The familiar figure of Selwyn Hopkins sat on the bench under the horse chestnut tree, gazing out over the estuary. 