noun
decayed tree; rotten wood
Refers to wood or a tree that has rotted and lost its structural integrity. Often used literally, but can carry a poetic or melancholic tone.
森の中で朽ち木を見つけた。
I found a decayed tree in the forest.
この朽ち木はもう薪にもならない。
This rotten wood can't even be used as firewood anymore.
noun
obscure, meaningless life
Metaphorical use, comparing a wasted or insignificant life to a rotting tree. Often appears in literary or reflective contexts. Cross-referenced with 朽ちる sense 2.
See also: 朽ちる
彼は自分の人生を朽ち木のように感じていた。
He felt his life was like a decayed tree—obscure and meaningless.
朽ちる is the verb meaning 'to decay' or 'to rot', while 朽ち木 is the resulting decayed tree or wood. Sense 2 of 朽ちる also carries the metaphorical meaning of dying in obscurity.
Compound of 朽ち (kuchi, the continuative form of 朽ちる 'to decay') + 木 (ki, 'tree, wood'). The reading くちき is a straightforward combination.