Plain English Meaning
An ILS approach that also gives you a continuous readout of how far you are from the runway, using equipment paired with the localizer.
Full Definition
An Instrument Landing System approach that has Distance Measuring Equipment co-located with the localizer, allowing the pilot to determine precise distance from the runway threshold throughout the approach. The DME signal is transmitted on a frequency paired with the ILS localizer frequency, so tuning the ILS automatically tunes the associated DME.
Context Anchor
Seen on instrument approach charts and in instrument flying discussions when an ILS approach also uses DME distance information.