regicides. After the second civil war in 1648, most army leaders despaired of reaching an agreement with the king that would be honoured and resolved to put him on trial. Fifty-nine signed Charles's death warrant in January 1649. At the Restoration, the remains of Cromwell, Ireton, and Bradshaw were taken from Westminster abbey and hanged at Tyburn. Of the 41 regicides still alive, 9 were put to death. Thomas Harrison, one of Cromwell's major-generals, told the court, ‘This was not a thing done in a corner.’

J. A. Cannon

reg·i·cide / ˈrejəˌsīd/ • n. the action of killing a king. ∎  a person who kills or takes part in killing a king.DERIVATIVES: reg·i·cid·al / ˌrejəˈsīdl/ adj.

regicide any of those who took part in the trial and execution of Charles I; after the Restoration, several of the regicides were tried and executed, and the bodies of Oliver Cromwell and others were dug up, drawn on a hurdle to Tyburn, displayed in their coffins on the scaffold, and finally buried under the gallows.

regicide1 one who kills a king. XVI. f. L. rēx, rēg- king + -CIDE1.
So regicide² (-CIDE2) killing of a king. XVII.