1
unable to understand (reason, motive, etc.)
1
to become known;to come to light;to be discovered
See also:
お里が知れる (おさとがしれる)
杳として行方が知れない。
Nothing whatever is known of him.
2
3
to clearly not amount to much;to be insignificant
See also:
たかが知れている (たかがしれている)
4
to be evident;to be obvious;to go without saying
as 知れたこと
5
to be very intense (of worry, hope, etc.);to be severe
as どんなに…か知れない, どれほど...か知れない, etc.