Quadraphonic is a term that typically refers to a sound system that has four channels of audio output. However, there are several other terms that can be used to describe similar audio technologies. For example, "surround sound" refers to any system that creates an immersive audio experience by placing speakers around the listener. "4.0 sound" is a similar term that specifically refers to four channels of audio output. "Multichannel sound" is another term that can be used to describe any sound system that has more than two channels of audio. Finally, "four-channel stereo" is a somewhat dated term that was commonly used in the 1970s and 1980s to describe quadraphonic sound systems.