noun
A person who secretly collects information about another country or organization. Often used in military, political, or espionage contexts. The term is somewhat formal and less common in everyday conversation than スパイ.
彼は戦時中、間諜として敵国に潜入した。
During the war, he infiltrated the enemy country as a spy.
その男は間諜の疑いで逮捕された。
The man was arrested on suspicion of being a spy.