Definition
A free ADS-B service that uplinks radar-derived traffic information from FAA ground stations to properly equipped aircraft. TIS-B sends data on aircraft that are detected by ATC radar but are not transmitting ADS-B Out themselves, so that ADS-B In equipped aircraft can see this traffic on their cockpit display alongside ADS-B-equipped traffic.
Plain English
It's a free ground-to-cockpit service that shows you nearby aircraft that radar can see but that aren't broadcasting their own position, so your traffic display gives you a more complete picture.
Context Anchor
Seen on cockpit traffic displays when an aircraft has equipment that can receive FAA traffic broadcasts.
Derivation
The name describes the function: 'Traffic Information Service' (data about other aircraft) delivered by 'Broadcast' (sent out from ground stations to any qualified receiver in range, rather than on individual request).
Why Pilots Care
It extends traffic awareness to non-ADS-B equipped aircraft, improving situational awareness and collision avoidance in mixed-equipage airspace.
Intuition Check
TIS-B is traffic information, not weather information. It may be discussed near data-link weather systems because it uses a similar broadcast path, but its purpose is to help show nearby aircraft.
Example Sentence 1
After installing an ADS-B In receiver, the pilot noticed several non-ADS-B aircraft now appeared on the traffic display thanks to TIS-B.
Example Sentence 2
TIS-B provided traffic data on a VFR aircraft that was not transmitting ADS-B Out.