a. Any of various Eurasian plants of the mustard family, especially white mustard, Indian mustard, and black mustard, which are cultivated for their pungent seeds and edible leaves.
b. A condiment made from the powdered seeds of certain of these plants.
2. A member of the mustard family.
3. A dark yellow to light olive brown.
4. Any of a group of toxic organic compounds that include mustard gas and the nitrogen mustards.
[Middle English, from Old French mustarde, from Latin mustum, must, unfermented wine; see MUST3.]
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.