In Traditional Chinese Medicine (TCM), xīn wèi refers specifically to the 'pungent' or 'acrid' flavor—one of the five fundamental flavors (along with sour, bitter, sweet, and salty) used to classify herbs, foods, and their physiological effects. The character xīn originally meant 'spicy' or 'sharp' and carries connotations of dispersing, warming, and promoting circulation; wèi simply means 'flavor' or 'taste'. Together, they denote a therapeutic property rather than just a sensory experience.

This term appears almost exclusively in TCM contexts—such as herbal prescriptions, dietary therapy, or diagnostic discussions—not in everyday cooking descriptions. For example, ginger and scallions are said to have xīn wèi because they help release exterior pathogens and warm the body. It is not synonymous with 'spicy' in the modern culinary sense (e.g., chili heat), which is more accurately described by là.