Recording audio in a format of continuous vibrations that are analogous to the original sound waves. Before audio recording became digital, sounds were "carved" into vinyl records or written to tape as magnetic waveforms. Contrast with digital audio.
Sound is literally carved into a phonograph record (top) because the groove undulations are analogous to the sound waves they represent. This 78 RPM record contained about four minutes of analog audio per side, compared to the CD, which holds from 80 minutes to 800 minutes of digital audio, depending on format (CD-DA or MP3).