noun
breakup; closure; end of a gathering
Polite euphemism for ending a formal or social event such as a party, meeting, wedding, or ceremony. Often used in set phrases like お開きにする or お開きになる.
そろそろお開きにしましょう。
Let's call it a night / wrap things up.
披露宴は三時にお開きになった。
The wedding reception ended at three o'clock.
閉会 is a formal, often written term for closing a meeting or conference, while お開き is a softer, spoken euphemism for ending a social gathering.
解散 means disbanding or breaking up a group, often used for formal dissolution of organizations or assemblies, whereas お開き is limited to ending events.
From the honorific prefix お + 開き (noun form of 開く 'to open'), originally a euphemism for 'opening' the way to leave, i.e., ending an event.