Definition of:speaker. A device that converts analog audio signals into the equivalent air vibrations in order to make audible sound. When CRT monitors were the norm, speakers designed for computers were shielded to avoid magnetic interference with the CRT's magnetic coil. device that converts analog audio signals into the equivalent air vibrations in order to make audible sound. When CRT monitors were the norm, speakers designed for computers were shielded to avoid magnetic interference with the CRT's magnetic coil.