知(し)れるto become known, to come to light, to be discovered, to be known, to be understood, to clearly not amount to much, to be insignificant, to be evident, to be obvious, to go without saying, to be very intense (of worry, hope, etc.), to be severe

辞書の定義

一段動詞, 自動詞
1.
to become known, to come to light, to be discovered
関連項目:
お里が知れる
一段動詞, 自動詞
2.
to be known, to be understood
usu. in the negative,
関連項目:
気が知れない
得体の知れない
一段動詞, 自動詞
3.
to clearly not amount to much, to be insignificant
関連項目:
高が知れている
一段動詞, 自動詞
4.
to be evident, to be obvious, to go without saying
as 知れたこと
一段動詞, 自動詞
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.