Definition
An autopilot mode that automatically maintains the aircraft at the pressure altitude it was at the moment the mode was engaged. The autopilot makes small pitch adjustments to keep that altitude constant, regardless of minor changes in airspeed or power.
Plain English
A button on the autopilot that tells the airplane: 'Stay at this altitude.' Once you press it, the autopilot flies the aircraft level at whatever altitude you were at when you pressed it.
Context Anchor
Seen on an autopilot control panel or flight display when using the autopilot during instrument flight, cruise, or level portions of a procedure.
Derivation
ALT is a common aviation shortening of altitude. Hold means to keep something steady, so altitude hold means keeping the aircraft at a set altitude.
Why Pilots Care
Reduces pilot workload during cruise and allows precise altitude management without constant manual corrections.
Intuition Check
ALT does not mean alternate here; it means altitude. HOLD does not mean wait; it means maintain the altitude already selected or captured.
Example Sentence 1
After leveling off at 7,000 feet, the pilot pressed ALT HOLD and the autopilot maintained that altitude for the rest of the cruise.
Example Sentence 2
With ALT HOLD engaged the airplane stayed at the assigned altitude even as the air became slightly turbulent.