conker
Concise Oxford English Dictionary © 2008 Oxford University Press:
conker/ˈkɒŋkə(r)/
▶noun Brit. the hard, shiny dark brown nut of a horse chestnut tree.
■ (conkers) [treated as sing.] a children's game in which each has a conker on a string and tries to break another's with it.
'conker' also found in these Oxford entries:

