Definition
The pitch axis, also called the lateral axis, is the imaginary line running through the airplane from wingtip to wingtip, passing through the center of gravity. Rotation around this axis is called pitch, and it is what raises or lowers the airplane's nose. Pitch is controlled by the elevator (or stabilator), which is operated by fore-and-aft movement of the control yoke or stick.
Plain English
The pitch axis is the side-to-side line through the airplane that the nose pivots up and down around. Pulling back on the yoke raises the nose; pushing forward lowers it.
Context Anchor
You see this term when learning the three airplane axes of movement and how the elevator changes the airplane’s nose-up or nose-down position.
Derivation
Lateral' comes from the Latin latus, meaning 'side.' The lateral axis runs side to side across the airplane, from one wingtip to the other. 'Pitch' is the older nautical word for the up-and-down motion of a ship's bow, carried over to aircraft.
Why Pilots Care
Understanding this axis lets a pilot use the elevators correctly to control climb, descent, and level flight attitude.
Analogy
A seesaw turns around a bar across its middle. In a similar way, the airplane pitches around a side-to-side line, with the nose moving up or down.
Intuition Check
Pitch here does not mean throwing something, making a sales pitch, or the highness or lowness of a sound. In this context, pitch means the airplane’s nose-up or nose-down rotation around its side-to-side axis.
Example Sentence 1
On rotation, the pilot applied gentle back pressure to pitch the nose up about ten degrees for the initial climb.
Example Sentence 2
The pilot applied back pressure to pitch the nose up and begin a climb, rotating the airplane about its lateral axis.