D defs.my
Entry 2 senses Webster, 1913

Regicide

/(rĕj"ĭ*sīd)/ · Reg·i·cide · IPA /ˈɹɛ.d͡ʒə.saɪd/
01 n. One who kills or who murders a king; specifically (Eng. Hist.), one of the judges who condemned Charles I. to death.
  1. 1.
    One who kills or who murders a king; specifically (Eng. Hist.), one of the judges who condemned Charles I. to death.(Eng. Hist.)
  2. 2.
    The killing or the murder of a king.