There aren't many readily used synonyms for the word "orthometric". This term is typically used in the field of geodesy and refers to the height above a specified reference surface, such as the geoid or ellipsoid. Some related terms that may be used instead include "geodetic height", "ellipsoidal height" or "vertical position". These terms all relate to a similar concept of measuring the vertical distance of a point above a certain reference surface. While there may not be direct synonyms for "orthometric", these related terms can be used interchangeably in context.