also: ぼうへん
noun
plotting to overthrow the government (by assassinating the emperor)
Archaic term for high treason, specifically a plot to kill the emperor and seize power. Associated with the historical legal concept of 八虐 (eight grave offenses). Sometimes read むほん.
See also: 八虐
謀反は八虐の一つとして最も重い罪とされた。
Plotting to overthrow the government was considered the gravest crime among the eight unpardonable offenses.
歴史書には、謀反を企てた貴族の名が記されている。
The names of nobles who plotted treason are recorded in historical documents.
反逆 is a broader term for rebellion or treason, not necessarily involving assassination of the emperor. 謀反 specifically refers to the archaic crime of plotting to kill the emperor.
八虐 is the historical legal category of eight grave offenses under the Ritsuryō system, of which 謀反 was the first and most serious.
From Middle Chinese-derived elements 謀 (plot) and 反 (rebel). The reading むへん is the older go-on reading, while ぼうへん is a later kan-on reading. The variant むほん reflects historical labial weakening.