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.
3) Cathedral of Saint John the Divine. This New York cathedral is the largest in the Americas and nearly in the world. Still unfinished, its website says the floor plan covers 11,200 square meters and the church has an overall volume of 480,000 cubic meters.