The term 'not stereo' refers to audio recordings that are not in stereo, meaning they are not recorded with two separate channels. The crossword solutions for this term are MONO (4 letters), HIFI (4 letters), and MONAURAL (8 letters). Mono is short for monophonic, which is a single-channel audio recording. HIFI stands for high fidelity, which is a type of audio recording that is of higher quality than standard recordings. Monaural is another term for monophonic, which is a single-channel audio recording.