great rebellion; large-scale uprising
Refers to a major, often violent, revolt or insurrection against authority. Typically used in historical or news contexts.
その国では大乱が起こり、政府が倒れた。
A great rebellion broke out in that country, and the government fell.
歴史の教科書に、農民による大乱の記述がある。
The history textbook contains an account of a large-scale uprising by peasants.
Compound of 大 (large, great) and 乱 (disorder, rebellion). The exact historical derivation is uncertain, but the word has been used in classical and modern Japanese to denote major uprisings.