The word "叛乱" is formed by combining the character "叛", which means to betray or revolt and is composed of "反" (against) and "半" (half), suggesting a betrayal of allegiance, with the character "乱", which means chaos or disorder and conveys the resultant turmoil. Together, they create a compound word where "叛" denotes the act of rebellion and "乱" emphasizes the chaotic state, resulting in the meaning of rebellion or insurrection.