Refers to the tree Aesculus hippocastanum or its seed. Often used in botanical contexts.
See also: セイヨウトチノキ
There is a large horse chestnut tree in the park.
The fruit of the horse chestnut looks like a chestnut, but it is not suitable for eating.
Standard kanji spelling for horse chestnut.
Katakana spelling, often used for plant names.
Compound of 馬 (uma, 'horse') and 栗 (kuri, 'chestnut'), likely a calque from English 'horse chestnut'.