Magic
n
- the art that, by use of spells, supposedly invokes supernatural powers to influence events; sorcery
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- any mysterious or extraordinary quality or power: the magic of springtime.
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Magic (2)
- a. the use of means (as charms or spells) believed to have supernatural power over natural forces
- a. an extraordinary power or influence seemingly from a supernatural source
b. something that seems to cast a spell
spell
n.
1. a. A word or formula believed to have magic power.
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formula
- an established form or set of words, as used in religious ceremonies, legal proceedings, etc
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- a. a method, pattern, or rule for doing or producing something, often one proved to be successful
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supernatural
adj.
- pertaining to or being above or beyond what is natural or explainable by natural law.
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Conclusion:
Using the contemporary definition of the word "magic", any device that, by use of a word or formula, supposedly does something that is above or beyond what is natural or explainable by natural law is magic. If we simplify, "Magic" is just stuff we can't/won't explain - e.g. just listen to the word "Magic" being used in Apple keynotesmarketing speech.
Many contemporary devices fit the bill by that definition. Semantics depend on what word the people from the past would actually use and what the exact meaning at the time it was used would be, but they would certainly realize that some devices are beyond their current understanding, just like they are beyond the understanding of most modern humans.