noun
in absolute secrecy; with utmost secrecy
Used adverbially as 極秘裏に to describe actions carried out under the strictest confidentiality. Often found in formal or official contexts.
その交渉は極秘裏に進められた。
The negotiations were conducted in absolute secrecy.
極秘裏に会議が開かれた。
A meeting was held with utmost secrecy.
Compound of 極秘 (top secret) and 裏 (back, hidden side), literally 'behind the scenes of top secrecy'. The reading ごくひり is a standard on'yomi combination.