Audio: A device with two variable impedance pads, developed to provide a constant impedance (generally 8 or 16 ohms) with respect to the amplifier and to control the output level for tweeters and midrange speakers. The L-pad was not intended to be used to control the higher currents of woofers. Because L-pads convert the energy not sent to the speakers into heat, they have largely been replaced by other types of controls, such as transformer-based volume controls.

a passive device which lets you control the output level of speakers without changing the impedance seen by the amplifier

a specialized potentiometer (fancy name for volume control) it's just a very low resistance usually high wattage pot (abbrev