- [countable]
the light-brown nut of the walnut tree that has a rough surface and a hard round shell in two halves 核桃；胡桃 
- (also walnut tree)[countable]
the tree on which walnuts grow 核桃树；胡桃树 - [uncountable]
the brown wood of the walnut tree, used in making furniture 核桃木；胡桃木 a walnut writing desk 胡桃木写字台
Word Originlate Old English walh-hnutu, from a Germanic compound meaning ‘foreign nut’.