Noun

1. The killing of one's brother (or sister).
2. A person who commits this crime.
   • 1936, H. A. L. Fisher, A History of Europe, Edward Arnold Publishers, p.376,

     The conversion of Russia to Christianity was effected, it would seem by a monster of cruelty and lust. That Vladimir (980 - 1015) was a fratricide, who maintained 3,500 concubines, has not prevented his canonization as a saint.

3. The killing of a comrade in arms or one who commits this act (intentionally or unintentionally).
   • 1999, Richard M. Swain, Lucky War: Third Army in Desert Storm, DIANE Publishing, p. 180,

     From January on, Third Army also spent a good deal of energy trying to solve the problem of fratricide, the killing or injuring of one's own forces by what is ironically called 'friendly fire,'...

Related terms

• (murder) homicide
• (murder of father) patricide
• (murder of king) regicide
• (military) friendly fire