Plain English Meaning
A recorded message that plays on a set radio frequency at busy airports, giving you the latest weather, which runway is in use, and other things you need to know before landing. You listen to it first, then tell the controller you have it so they don't have to repeat it.
Full Definition
A continuous broadcast of recorded non-control information at busier airports, providing the current weather, active runway(s), approach in use, NOTAMs, and other essential arrival or departure data. Pilots listen to ATIS before contacting approach or tower so the controller does not have to repeat routine information to each aircraft. Each broadcast is identified by a phonetic letter (Alpha, Bravo, Charlie, etc.) that increments with every update, and having received the current letter on initial . At airports without ATIS, the same information is obtained directly from the tower or, at non- fields, from a () call or an (AWOS) / (ASOS) broadcast.