Definition
HDG is the standard cockpit and avionics abbreviation for heading — the direction the aircraft's nose is pointing, measured in degrees clockwise from north (000° to 359°). On glass cockpit displays, HDG typically labels the heading bug, the heading readout at the top of the HSI or PFD compass arc, or the HDG mode of the autopilot, which commands the aircraft to turn to and hold a selected heading.
Plain English
HDG is the short label for 'heading' — the direction the nose of the airplane is pointing, shown as a number from 000 to 359 degrees. You'll see it on the screen above the compass and as a button or mode on the autopilot.
Context Anchor
Seen on instrument displays, heading indicators, and flight display labels such as those shown with trend indicators.
Derivation
HDG is a shortened cockpit-display form of “heading.” “Heading” comes from the idea of the aircraft’s head, or nose, pointing in a direction.
Why Pilots Care
Following the assigned heading keeps the aircraft on the intended route and prevents navigation errors.
Intuition Check
Do not read HDG as the airplane’s exact path over the ground. HDG is where the nose points; wind can make the airplane move along a slightly different path.
Example Sentence 1
After takeoff, the controller said, 'Turn left, HDG 270,' so I twisted the heading bug to 270 and the autopilot in HDG mode rolled the airplane into the turn.