Pending the assent of the parties involved, or a higher authority; subject to agreement by other parties and (now usually) to finalization of the details.
A proposal or resolution referred to other parties for approval or sanction; = "referendum".
Relating to or designating a decision, arrangement, etc., made on such a basis; that is subject to agreement by other parties.
Early 18th century; earliest use found in Abel Boyer (?1667–1729), lexicographer and journalist. From post-classical Latin ad referendum pending the assent of the parties involved, subject to agreement from classical Latin ad + referendum.