1. Capable of burning, corroding, dissolving, or eating away by chemical action.
2. Sarcastic or cutting; biting: “The caustic jokes ... deal with such diverse matters as political assassination, talk-show hosts, medical ethics” (Frank Rich).
3. Given to making caustic remarks: a caustic TV commentator.
1. A caustic material or substance.
2. A hydroxide of a light metal.
3. The enveloping pattern formed by light rays reflecting or refracting from a curved surface.
[Middle English caustik, from Latin causticus, from Greek kaustikos, from kaustos, from kaiein, kau-, to burn.]
caus·tici·ty (kô-stĭsĭ-tē) n.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.