"High def" is an informal term used to describe high definition video or audio. However, there are numerous synonyms to describe this high quality media. These synonyms include "4K," which is a reference to the resolution of the video. Other terms such as "ultra-high definition," "supersize," "high clarity," and "high resolution" can also be used to describe high def. These synonyms are often used in marketing materials or in technical specifications for media devices. Regardless of the synonym that is used, all refer to the same thing - high quality audio or video that provides an immersive and engaging experience for the user.