Definition
The horizontal reference lines on an attitude indicator, located above and below the artificial horizon, that show the aircraft's nose-up or nose-down angle in degrees relative to the horizon.
Plain English
The little lines on the attitude indicator that tell you how far the nose is pointing up or down compared to level flight.
Context Anchor
Seen on the attitude indicator during instrument flying, especially when setting or checking climb, level, or descent attitudes.
Derivation
Pitch' here refers to the up-and-down rotation of the aircraft's nose around its lateral axis (the same sense as a ship pitching in waves). The 'marks' are simply the printed reference lines on the instrument face that let the pilot read that pitch angle.
Why Pilots Care
They let the pilot maintain a precise climb, descent, or level attitude when outside visual references are unavailable.
Analogy
They work like the marks on a ruler: instead of judging by eye alone, you compare the aircraft symbol to measured lines.
Intuition Check
“Pitch” does not mean sound or throwing here. It means the aircraft’s nose-up or nose-down position compared with the horizon.
Example Sentence 1
After the missed approach call, she pulled the nose up to the 10-degree pitch mark and held it there during the climb.
Example Sentence 2
During the approach briefing, the instructor pointed out the pitch marks used for the stabilized descent.