The characters literally combine to mean “rubbing shoulders and connecting heels.” This creates an unforgettable image of a crowd in motion, where people are packed together both side-to-side (rubbing shoulders) and front-to-back (heels connecting with the person in front).
In a country with the world's largest population, massive crowds are a common feature of daily life, especially in cities and during public holidays like the Spring Festival or National Day Golden Week. Idioms like 摩肩接踵 are not just abstract descriptions; they capture a real, shared sensory experience for many Chinese people. The term evokes the sights, sounds, and feeling of being in a bustling temple fair, a packed subway station, or a famous tourist landmark swarming with visitors. While an English speaker might say a place is “packed like sardines,” that phrase emphasizes being static and crammed into a tight space. 摩肩接踵, by contrast, often implies a crowd that is moving or flowing, like a river of people. The “connecting heels” (接踵) part is key—it highlights the difficulty of moving forward in such a dense throng. This idiom reflects a cultural familiarity with, and a specific vocabulary for, describing large-scale public gatherings and the feeling of being part of an immense collective.
摩肩接踵 is a formal and literary idiom (成语 chéngyǔ). You are more likely to encounter it in written Chinese (news articles, books, travel blogs) or in more formal speech than in a casual, everyday conversation.