Geoengineering is short for “geological engineering,” or what could otherwise be called geological modification.  Technically, we could categorize planetary modifications as geo- or litho-, atmo-, bio-, or hydro-engineering.  However, I am more inclined to place them all under the term “environmental modification.” 

Environmental modification, also known as ENMOD, reached its apex during the Vietnam War, but the United Nations ultimately banned it in 1976.  Originally prohibiting the “modification of the natural environment for use as a weapon of war,” the ban later expanded to include “acts of war injurious to the natural environment.”  The United States, along with forty-seven other nations, are signatories to this treaty, which is formally titled the “Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques.”  The first two articles state:
1. Each State Party to this Convention undertakes not to engage in military or any other hostile use of environmental modification techniques having widespread, long-lasting or severe effects as the means of destruction, damage or injury to any other State Party.

As used in article 1, the term "environmental modification techniques" refers to any technique for changing - through the deliberate manipulation of natural processes - the dynamics, composition or structure of the Earth, including its biota, lithosphere, hydrosphere and atmosphere, or of outer space.

Climate Supremacy: an interview with Mr. Byrne
Ontario Association of Landscape Architects, Ground Magazine, 21 Politics (2013), 16-19.
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