regicide

regicide
/ˈredʒɪsaɪd; `rɛdʒəˌsaɪd/ n
1 [U] crime of killing a king 弑君罪.
2 [C] person who commits or helps to commit this crime 弑君者; 弑君罪犯或从犯.

牛津英汉双解词典