With regards to the mute button on tvs and radios and such, what does ATT stand for?
It might be short for attenuate which means to become weaker. Older radios used to say this, but I’ve never seen it on a TV.
“Att” is used to reroute the audio signal through what’s commonaly called a “pad”, most commonly -20db but sometimes an adjustable dial, to knock the level down.
My car stereo has this button. Hit it once and the volume goes low. Hit a second time and it returns to the previous setting slowly so as not to damage the speakers.