To remove someone from royal power or position; to depose or dethrone a reigning monarch or ruler.
From 'de-' (to remove) plus 'reign,' an archaic or poetic term used primarily in historical or literary contexts to describe the overthrow of rulers.
This is an old-fashioned word, but it perfectly captures a specific kind of political violence—not just killing a king, but formally removing him from power, which was sometimes negotiated rather than violent.
Complete word intelligence in one call. Free tier — 50 lookups/day.