Combining them, the literal translation is “no movement in the heart.” This paints a vivid picture of someone whose inner emotional world remains perfectly still, even when faced with something that should cause ripples of feeling.
In Chinese culture, which often places a high value on empathy, social harmony, and consideration for others (concepts related to 人情 rénqíng), being 无动于衷 is a serious criticism. It's not just a description of a neutral state; it's a judgment of character. To be unmoved by the suffering of others, a heartfelt plea, or a moral crisis can be seen as a failure of one's social and moral duty. A Western equivalent like “apathetic” can sometimes describe a general state of disinterest (e.g., “politically apathetic”). However, 无动于衷 is almost always situational and accusatory. It's used to call someone out for their lack of response in a specific moment. For example, while an American might say “he's apathetic” as a general personality trait, a Chinese speaker would more likely say “he saw the accident and was 无动于衷,” highlighting the failure to react appropriately in that specific context. This reflects a cultural expectation to be present, engaged, and empathetic towards one's immediate community and surroundings.
无动于衷 is a common idiom used in both spoken and written Chinese. It is almost always used to express criticism or disappointment and carries a strong negative connotation.