Plain English Meaning
It's the airport information report (winds, runway in use, weather, etc.) sent to the cockpit as text or recorded audio over a data link, instead of the crew tuning a radio to listen to a looping voice broadcast.
Full Definition
A data link service that delivers Automatic Terminal Information Service (ATIS) broadcasts as text and/or synthesized voice directly to the aircraft, rather than requiring the crew to listen to a continuously looping VHF voice broadcast. Digital ATIS (D-ATIS) provides the same airport information — active runways, approaches in use, weather, NOTAMs, and other — but transmits it through a - data link so the crew can read it on a cockpit and reduce .