like who thought hmmmm
when a plane is taking off it looks like it is rotating...?

It is not a rotation in a spinning or orbiting sense. The basic definition of rotate is to cause to turn about an axis. During a takeoff roll, ''rotate'' is the point at which the pilot begins to pivot the longitudinal axis of the airplane about the main landing gear. This ''rotation'' continues until the point of liftoff.

Yeah, l agree, it may not sound like the best term, but we could probably make the same argument for any other term that could be used.

EDIT: l purposely meant the longitudinal axis. l did not say that the plane rotates AROUND the longitudinal axis. l said that the longitudinal axis (the line from the nose to the tail) pivots around the main landing gear, meaning the line of the longitudinal axis is what is changing.

l admit that probably was not the best term to use there, but during rotation, the plane does not pitch about the lateral axis either. If u watch an airplane on rotation, imagine a line going from wingtip to wingtip. You will see that the airplane is not ''pivoting'' on this line the way it does in the air. Until the plane is in the air, the main landing gear is the pivot point (fulcrum) because the ground is affecting it. Once airborne & the ground has no effect on where the aircraft is pivoting, the pitch ''pivots'' about the lateral axis, or the ''wingtip to wingtip line which goes through the CG.

The guy above is mostly right, but when a plane rotates in the manner you are speaking of, it is around its horizontal axis, not it is longitudinal one. A simple misconception. The longitudinal axis runs from nose to tail, to rotate around that axis would be ''rolling''. But l am just debating semantics, a petty thing.

The guy above me (Sean) is kinda right, but the axis that extends crosswise (wingtip through wingtip) is called the lateral axis not the ''horizontal''
(The elevators rotate the airplane around the lateral axis)

Edit: MALIBU CANYON is correct, l should have said the lateral axis is an imaginary line passing through the center of gravity & parallel to a line joining wingtip to wingtip so l too am guilty of being kinda right . l was too hung up on ''Horizontal'' to explain fully. My bad.

During takeoff, what is called ''rotate'' is precisely when the plane begins to rotate. Before rotation, the plane is nose is pointing roughly horizontally. During rotation, the plane is nose is rotated upward several degrees. When describing maneuvers, we generally ignore the plane is forward motion because that is a constant for most maneuvers. The rotation normally precedes liftoff, so we're not describing the upward movement of the plane.

Because the plane 'rotates' on its pitch axis to point up and take off. l guess it could also mean that you 'rotate' the elevators up.

--Because the aircraft is rotating about an axis.

Rotation does not apply only to the takeoff maneuver. It applies in the air and after touchdown, too.

Coffebuzz is absolutely correct. An aircraft 'rotates' about the main landing gear axle center line. Even in aircraft with conventional landing gear (taildraggers).

The word is ''rotation not pivot. And the lateral axis is NOT defined as wing tip to wing tip. The axes are supposed to intersect. Consider a swept wing aircrcaft.
Back to the original question: l think the ''rotation'' terminology is better explained with respect to the lateral axis, all ''pivoting'' issues aside.