a. The killing of one's brother or sister.
b. One who has killed one's brother or sister.
2. The accidental killing of an ally caused by a discharge of a military weapon.
[Middle English, from Old French, from Latin frātricīdium and frātricīda : frāter, frātr-, brother; see bhrāter- in the Appendix of Indo-European roots + -cīdium and -cīda, -cide.]
frat′ri·cidal (-sīdl) adj.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 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.