Definition
A terminal radar approach control facility that is physically located inside the airport's control tower cab, rather than in a separate building or remote site. Controllers working radar approach control duties share the same room as the local and ground controllers running the tower itself.
Plain English
A radar room for handling arriving and departing aircraft that sits right inside the tower cab at the top of the control tower, instead of being housed somewhere separate.
Context Anchor
Seen in FAA acronym lists, facility descriptions, and instrument procedure material that identifies the air traffic control unit serving an airport.
Derivation
The name simply describes the arrangement: a Terminal Radar Approach Control (commonly called a TRACON) that has been placed in the tower 'cab' — the glass-walled room at the top of the control tower where tower controllers work.
Why Pilots Care
Knowing a field has a TRACAB tells you that approach control and tower services are run from the same facility. Hand-offs can be quicker, and the controller working your arrival may be sitting next to the one who will clear you to land.
Intuition Check
Do not assume TRACAB means a separate radar building. In this term, the radar approach control function is located in the tower cab.
Example Sentence 1
At airports with a TRACAB, the radar approach controllers and tower controllers share the same room at the top of the tower.
Example Sentence 2
At smaller airports TRACAB often combines tower and approach control in the same cab.