Definition of "semidome"

At Holy Cross Catholic Church on West 42nd Street, opposite the Port Authority Bus Terminal, the uninviting Romanesque exterior is in stark contrast to the airy sanctuary, with its great open space and a main altar set in a lovely semidome and illuminated by nine stained-glass panels.

2009 April 12, Tanya Mohn, “Blessings Over Broadway”, in New York Times‎