The word ecumenical comes from a Greek word that means pertaining to the whole world. It primarily describes a pluralist religious ethic, though in Christianity it only applies to the Christian church, and describes the pursuit of unity in the Christian world, between Christian denominations, and the universality of the Church.
In the Catholic and Eastern Orthodox churches an ecumenical council is a council of nearly all bishops of the whole church, capable of infallible decisions on theological questions. Catholics construe "the whole church" as including only Catholics. Eastern Orthodoxy construes it as including only, and with the consent of all of, the Orthodox which, they contend, since the Great Schism, consists of only the Eastern Orthodox; they call the Patriarch of Constantinople the "Ecumenical Patriarch" and "first among equals" - he has juristiction within his patriarchate and in those other parts of the world without another patriarch.
Hinduism is a religion that some would argue is inherently ecumenical and teaches a fundamental doctrine of multilateralism in regards to truth and spirituality. Hinduism teaches that, in essence, all religious, philosophical and spiritual paths when followed with a common base of human morality and love will reveal truth to the seeker, regardless of professed creed. This is largely based on a passage from the Vedas which states, "Ekam sat, viprah bahudha vadanti", or, "Truth is one, but the wise call it by many names".
See also Ecumenism.