You can be confident that you won't need that definition in your own usage unless you decide to write an 18th century character or something.
To add to the etymology links (I was also intrigued):
https://www.grammarphobia.com/blog/2013/08/terror-terrific.h...
https://genius.com/Herbert-morrison-hindenburg-disaster-broa...
This posting [1] puts the usage change from around 1880-1930. I've always taken the modern usage to mean unusually fine/magnificent.
[1] https://english.stackexchange.com/questions/38606/what-gave-...
You can be confident that you won't need that definition in your own usage unless you decide to write an 18th century character or something.
To add to the etymology links (I was also intrigued):
https://www.grammarphobia.com/blog/2013/08/terror-terrific.h...