Definitions of supernatural courtesy Merriam-webster..
"of or relating to an order of existence beyond the visible observable universe"
In other words, any order in the universe we are unaware of is considered to be supernatural.
"departing from what is usual or normal especially so as to appear to transcend the laws of nature"
Note that just because something appears to transcend the laws of nature does not imply that it does.
"attributed to an invisible agent (as a ghost or spirit)"
There are forces we can't see that have an effect on things. How does the radio work? Antenna television? Wifi? Hitherto unknown or imperceptible forces?
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Most people are superstitious. People who think they are rejecting all forms of superstition tend to be, ironically, very superstitious themselves. Denying God, as an example, is very superstitious, but there are plenty of God deniers who like to flaunt their alleged rationality while mocking either real or perceived superstitions of others.