noun
treason; conspiracy against one's country
A legal term referring to the crime of conspiring with a foreign power to harm one's own country. Rare in everyday conversation; mainly encountered in legal or historical contexts.
外患罪は、国家反逆の重罪として扱われる。
Treason is treated as a serious crime against the state.
反逆罪 is a broader term for rebellion or insurrection against the state, while 外患罪 specifically involves collusion with a foreign power.
Compound of 外患 (foreign threat) + 罪 (crime). The exact historical derivation is uncertain; the term is a legal coinage.