Industries have their own jargon. Outsiders don’t get to redefine these words, nor do we get to cherry-pick definitions that support our bias.
Within the surveying industry, the word “level” has a very specific meaning. Using a dictionary in an attempt to make claims about surveying is disingenuous at best and most likely called called lying.
Surveying has defined “level” as the curved surface of the earth. For example in the book A Treatise on Practical Surveying level is clearly defined as a curved surface:
The true level is a curve conforming to the surface of the earth; as ABG.
The apparent level is a tangent to that curve; as ADE.
In the centuries since this book was first published in the 1700’s the technical definition of level has improved. Often a distance above Mean Sea Level is measured relative to WGS84. The WGS 84 datum surface is an oblate spheroid with equatorial radius 6378137.0 meters at the equator. The polar radius is 6356752.3142 meters.
Level is a curved surface related to the curving surface of the earth. When reading documentation related to surveying note that water does always find it’s level. A curved surface.