'Hēng shēng' literally combines 'hēng' — a verb meaning to hum, grunt, or snort — and 'shēng', meaning 'sound' or 'voice'. Together, they form a noun referring specifically to a short, low-pitched, involuntary vocalization expressing mild disapproval, impatience, skepticism, or physical discomfort. It’s not a full word but a vocal sound, often emitted through the nose with closed or partly closed lips.

This term is commonly used to describe human expressions of dismissive attitude (e.g., responding to an unreasonable request), but it also appears frequently in animal behavior descriptions — especially for pigs, horses, or dogs making guttural nasal sounds. Unlike longer interjections like 'hmpf' or 'tch', 'hēng shēng' emphasizes the acoustic quality and physical origin of the sound, and is more literary or descriptive than conversational.