Webster Dictionary(0.00 / 0 votes)Rate this definition: 1  Hypo-. a prefix signifying a less quantity, or a low state or degree, of that denoted by the word with which it is joined, or position under or beneath. 2  Hypo-.
Confidence votes 25. St Patrick's Cathedral in New York City. ***Actually, the Basilica of the National Shrine of the Immaculate Conception in DC is larger than St. Patrick's in NYC. The National Shrine is the largest Roman Catholic church in the U.S., and one of the 10 largest Roman Catholic churches in the world.
See Also: - Largest Religious Groups in the U.S.A. - See how the Catholic Church compares in size to other major religious groups in the United States. (Includes some maps.). - Religious Affiliation of History's 100 Most Influential People-Catholicism is represented more than any other religion on this list.