1. The ability to learn facts and skills and apply them; especially, when this ability is highly developed.
2. The capacity to acquire and apply knowledge or the faculty of thought and reason.
3. Information about secret plans or activities; especially, those of foreign governments, the armed forces, business enemies, or criminals.
4. Etymology: from Latin intelligent-, formed from intellegere,, “to perceive, to discern”; from inter-, “between” plus legere, “to choose, to read”.

1. A worldwide U.S. Air Force network which has fixed stations, specially equipped aircraft, and reconnaissance satellites to monitor and record enemy electromagnetic emissions. 2. Technical and geolocation intelligence derived from foreign noncommunications electromagnetic radiations emanating from other than nuclear detonations or radioactive sources.
3. Electronic systems, apparatus, and operations for obtaining information concerning a military enemy's capabilities, intentions, plans, and order of battle.