conker vs horse chestnut

conker and horse chestnut both are nouns.

Word	Noun	Adjective	Verb	Adverb
conker	Yes	No	No	No
horse chestnut	Yes	No	No	No

As nouns, conker and horse chestnut are synonyms defined as:

conker and horse chestnut: the inedible nutlike seed of the horse chestnut

Other synonyms of conker include buckeye.

conker (noun)	horse chestnut (noun)
the inedible nutlike seed of the horse chestnut	tree having palmate leaves and large clusters of white to red flowers followed by brown shiny inedible seeds
	the inedible nutlike seed of the horse chestnut