Wikipedia
Semi-dome
A semi-dome, also called a "half-dome", is the term in architecture for half a dome ("cut" vertically), used to cover a semi-circular area. Similar structures occur in nature.
Usage examples of "semi-dome".
Whatever the mosaicists could conceive for the dome and semi-domes and arches and walls in this place would be lit as no other surfaces in the world were lit.
A stunning twenty-foot-wide semi-dome crowns the apse, with a vaulted ceiling, stuccoed, white ribs picked out in regal hues- crimson, Tyrian purple, richest blues.