To the Post: "Conciliar" is not a translation of "Catholic" by any means, as described in subsequent replies. "Universality" is another word that that is synonymous with the Church's understanding of "Catholic." Also, "Catholic" is not used as a proper noun in the Creed, you can tell your inquiring friends; and advise them that this is the 4th century "Symbol of Faith," or Creed, promulgated when the Church was one; prior to the Great Schism and the Protestant Reformation.
This article of the Creed doesn't name the church, but describes it, it is "One," it is "Holy," it is "Catholic," as defined above, and it is "Apostolic." Don't forget to point out the difference in the Creed from the Western Churches, "And in the Holy Spirit, the Lord, the Creator of Life, Who proceeds from the Father, Who, together with the Father and the Son, is worshiped and glorified..." The distinction in this article, is the primary reason for the schism between the Roman Catholic Church and the Eastern Orthodox Church.
The writings of the Church Fathers (first several centuries) refer to the Church both as "Catholic" and as "Orthodox." In the end, we consider it the Christian Church. Liturgically, we refer to Eastern Orthodox Churches, or the Holy Orthodox Churches, as "the Holy Churches of God," (see the 2nd petition of the Great Litany of the Divine Liturgy).
Fr. John Meyendorf, of blessed memory, had written that the ethnic epithets (Greek, Bulgarian, Serbian, etc.) began in the late 17th and 18th centuries, when ethnic movements in the Balkan States were fomenting nationalist revolutionary sentiment, some within the Orthodox Churches, from the Ottoman Empire, in order to promote ethnic nationalism.