Antonyms for the word "aero-nautical" include words that describe things that are not related to aviation or flight. These words could include "terrestrial," "grounded," "land-based," or "non-flying." Additionally, other antonyms may include words that describe things that are opposed to or in opposition to aviation or flight, such as "anti-aviation," "anti-aeronautics," "opposing-flight," or "non-airborne." Finally, antonyms could include words that describe things that are not advanced or modern in terms of technology, such as "primitive," "archaic," or "obsolete." Ultimately, in the absence of the prefix "aero," antonyms for "aero-nautical" describe things that are not airborne, high-tech, or related to the field of aviation.