The term 'LESS THAN QUADRAPHONIC' refers to a type of audio system that has fewer than four channels. The crossword solution for this term is 'STEREO, ' which stands for 'sound technology with electromagnetic recording output.' STEREO is a two-channel audio system that produces sound from two separate sources, usually two speakers. It is the most common type of audio system and is used in many consumer products such as televisions, radios, and computers.