Conkers are round brown nuts which come from horse chestnut trees.
[British]
2. uncountable noun
Conkers is a children's game in which you tie a conker to a piece of string and try to break your opponent's conker by hitting it as hard as you can with your own.
[British]
conker in British English
(ˈkɒŋkə)
noun
an informal name for horse chestnut (sense 2)
conker in American English
(ˈkɑŋkər)
noun British
1. [pl., with sing. v.]
a child's game played with horse chestnuts tied to strings
2.
a horse chestnut
Word origin
Brit dial., orig., a snail shell (< conch + -er): the game was orig. played with shells