She watches him plane the surface of a walnut board.

她看着他刨一块胡桃木板。

《柯林斯英汉双解大词典》

One of the first display cases houses something that looks like a walnut or a fruit pit;

在首批展示盒中，有个展品貌似一个核桃或果核；

youdao

With a brain "the size of a walnut," as she puts it, the birds display what appears to be the cognitive potential of a young child.

她认为：这些大脑只有核桃大小的小鸟表现出的却是一个小孩可能会学会的认知能力。

youdao

In the fields, a walnut face under a conical coolie hat gazed at the foreign visitor.

BBC: Here be dragons

And how nice that nearby was the bread and the milk and a walnut snuffbox full of tobacco!

NEWYORKER: So It Is in Life

Prostatitis is swelling and inflammation of the prostate gland, a walnut-sized gland located directly below the bladder in men.

CNN: Prostatitis