An "input jack" is a small hole on a device, like a computer or a music player, where you can plug in a cord or cable to connect something to it, like headphones or a microphone. Full definition
A six - speaker radio system is standard and includes an auxiliary input jack for portable audio players. (speedsportlife.com)
Keep the kids happy with this rear seat 9 - inch DVD monitor, remote control, infrared wireless headphones (2) and auxiliary video input jack. (mitsubishicars.com)
This little adapter makes it easy to play music wirelessly to older powered speakers that have a 3.5 mm input jack. (ecoustics.com)