Detached
I was riveted to my father's agony.
it is riveted in.
No, the opposite of a definition is certainly not always true. That would depend on the definitions and the meaning of the opposite.
opposite
Undefinition
specific
The opposite of download
what is the opposite of brooding
I found myself riveted as I listened to the speech.
Generosity, possibly.
Adjacent
Lady GaGa's costumes are so gaudy that many people are riveted by her.