A caustic chemical burns or destroys things, especially anything made of living cells.

a caustic substance 腐蚀性物质

A caustic remark or way of speaking is hurtful, critical, or intentionally unkind.

caustic comments 尖刻的评论

She's famous in the office for her caustic wit. 她说话刻薄机智，在办公室是出了名的。