noun
joint meeting of both houses
A formal conference between the two chambers of a bicameral legislature, such as the Japanese Diet's House of Representatives and House of Councillors, often convened to resolve disagreements.
予算案の不一致を解決するため、両院合同協議会が開かれた。
A joint meeting of both houses was held to resolve the disagreement over the budget bill.
Compound of 両院 (both houses) + 合同 (joint) + 協議会 (conference). The term is a direct description of its function in a bicameral parliamentary system.