noun
chargé d'affaires
A diplomatic rank below ambassador; the head of a diplomatic mission in the absence of an ambassador, or a lower-ranking envoy.
大使が不在の間、代理公使が大使館を運営した。
While the ambassador was away, the chargé d'affaires ran the embassy.
大使 is a full ambassador, the highest-ranking diplomatic representative, while 代理公使 is a lower rank or temporary head of mission.
公使 is a minister (envoy), a rank above chargé d'affaires but below ambassador; 代理公使 is specifically a chargé d'affaires, often acting in place of an ambassador or minister.
Compound of 代理 (dairi, 'acting, proxy') and 公使 (kōshi, 'minister, envoy'). The term is a direct translation of the French 'chargé d'affaires'.