恼 means 'to be annoyed, irritated, or angry' — a verb describing a state of irritation or rising anger. It can also be used causatively ('to annoy someone'), though that sense is less common as a standalone verb and more often appears in compounds like 惹恼 (to provoke anger). In written and formal Chinese, 恼 is frequently part of disyllabic words such as 烦恼 (annoyed/worried), 恼怒 (furious), and the idiom 恼羞成怒 (to become angry from embarrassment).