"Ǒu nì" is a formal medical term meaning "nausea and vomiting" — two related gastrointestinal symptoms that often occur together. The character 呕 (ǒu) means "to vomit," while 逆 (nì) literally means "to go against" or "to rebel," and here conveys the idea of abnormal upward movement of stomach contents, contrary to normal downward digestion. Together, they form a compound noun used primarily in clinical contexts, traditional Chinese medicine (TCM), and medical literature to describe this specific symptom complex.

This term is not commonly used in everyday casual speech; native speakers typically say 恶心呕吐 (ě xīn ǒu tǔ) or just 吐 (tù) for vomiting. Ǒu nì appears in diagnoses, prescriptions, patient histories, and TCM patterns like 肝胃不和 (gān wèi bù hé, 'disharmony between liver and stomach') where it reflects an underlying imbalance causing upward rebellion of qi. It carries a clinical, slightly technical tone and implies a pathological process rather than transient discomfort.