In a manner relating to astronauts, space travel, or the technical aspects of spaceflight and exploration.
From 'astronautical' plus '-ly' to form an adverb. This word is rarely used in modern English, as speakers prefer describing spaceflight with other constructions.
This adverb is so rarely used that it's practically extinct—a reminder that just because you can make a word grammatically doesn't mean the world will adopt it!
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