轰轰 is a reduplicative onomatopoeia that imitates a loud, continuous booming or roaring sound, like thunder or explosions. It is also used figuratively to describe events or actions that are grand, vigorous, or carried out with great momentum, most commonly in the set phrase 轰轰烈烈 (hōng hōng liè liè, 'vigorous and grand'). As a reduplicative adverb or adjective, it typically modifies verbs or nouns in literary or formal contexts.