What does the acronym HMD mean in virtual-reality hardware?

In virtual-reality hardware, HMD means head-mounted display.

A head-mounted display is a device worn on the head that places one or more screens in front of the user’s eyes. In VR, the display normally shows separate images to the left and right eyes, creating stereoscopic depth. Sensors also track head movement so the rendered scene can change as the user looks around.

Modern VR HMDs commonly include lenses, displays, motion sensors, speakers, microphones, and cameras. Some connect to a computer or console, while standalone models contain their own processor and battery. The phrase is broader than virtual reality: augmented-reality and mixed-reality glasses can also be described as head-mounted displays.

HMD is a hardware description, not the name of a particular product. Oculus Rift, HTC Vive, PlayStation VR, and Meta Quest are product families that use head-mounted-display technology, but their tracking methods and computing requirements differ.