/ ˈfrætrɪsaɪd; NAmE / noun [ U , C ]
1.
( formal ) the crime of killing your brother or sister; a person who is guilty of this crime
—compare matricide , parricide , patricide
2.
the crime of killing people of your own country or group; a person who is guilty of this crime
► frat·ri·cidal / ˌfrætrɪˈsaɪdl; NAmE / adjective :
to be engaged in a fratricidal struggle
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WORD ORIGIN
late 15th cent. (denoting a person who kills their brother or sister, derived from Latin fratricida ): the primary current sense comes via French from late Latin fratricidium , from frater brother + -cidium , from caedere kill.