“入木三分”，汉语成语，字面意思是“enter three-tenths of an inch into the timber”，形容书法笔力刚劲有力（written in a forceful hand），也比喻对文章或事物见解深刻、透彻，可以用“penetrating；profound”表示。

例句：

他的分析真是入木三分。

His analysis was really penetrating.

这个真实的故事把两个年轻人的冷酷残忍刻画得入木三分。

The cold, hard cruelty of two young men is vividly brought to life in this true story.

这位书法家的字苍劲有力，入木三分。

This calligrapher writes a forceful hand, with bold and vigorous strokes.