imperial seal; privy seal
Refers specifically to the seal of the Emperor of Japan, used for official state documents. A formal, historical term.
The imperial seal is a stamp used by the Emperor when performing acts of state.
privy seal; imperial seal
From 御 (honorific prefix) + 璽 (seal). The character 璽 originally referred to the imperial seal in Chinese, and the term was adopted into Japanese for the same purpose.