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.
St. Peterâs Basilica. The largest cathedral in the world is also one of Roman Catholicismâs holiest sites. St. Peterâs Basilica in the Vatican City was consecrated in 1626. Some of Europeâs most important architects contributed to its construction, including Michelangelo and Carlo Maderno.