Hi-res audio
Digital audio with a higher sample rate or bit depth than CD's 44.1 kHz and 16 bits — and a never-ending argument about whether anyone can hear it.
The Japan Audio Society gave the term a formal definition and a gold sticker in 2014: at least 24 bits and 96 kHz, with the whole chain required to reach 40 kHz. The idea predates the sticker. SACD in 1999 and DVD-Audio in 2000 promised the same thing and achieved roughly the same commercial result, namely nothing.
In the studio the extra resolution earns its keep: 24 bits buys headroom while recording, and higher sample rates reduce aliasing in non-linear plugins. As a delivery format it's harder to defend. In 2007 Meyer and Moran had listeners compare SACD against the same material squeezed through a CD-quality bottleneck, and nobody could tell them apart. Xiph founder Chris Montgomery pointed out in 2012 that 192 kHz can even sound worse, since ultrasonic content causes intermodulation distortion in amps and speakers.