IT IS NOT:
notably connected with religion
fictional, mythical or legendary
connected with science
connected to a famous saying or cliche
made of words
notably involved with fish
an emotion
The Giant Rat of Sumatra
dream-like
something negative like silence or emptiness
an event
a piece of music
a period of time
the sound of silence
a reflection.

IT IS:
something that can be seen or heard, both directly, and very much, indirectly.
CLUE: It did not exist before the twentieth century.

Raak - Yyyyyyyyy - no.
Chalky - If it is possible to see or hear this thing directly, then there are places on this earth where one can do so, although not many. In theory, one could see or hear it indirectly anywhere.
Kim - No. But getting a little closer...