literally "stones from other hills"; a metaphor for using outside help, such as other people's advice, experiences, or criticisms, to help correct one's own faults or improve oneself

To be able to; to be possible; describes having the capacity or a use for something.

(literary) to work on material; to process; to polish or refine, as in the phrase 它山之石，可以攻玉 tā​shān​zhī​shí​kě​yǐ​gōng​yù

precious stone that is hard, translucent, and lustrous, including both nephrite and jadeite; used for jewelry and carving