
1) Type of arch
Found on
https://www.crosswordclues.com/clue/groin-vault

Gajah Mada (d. circa 1364) was, according to Javanese old manuscripts, poems and mythology, a famous military leader and prime minister (mahapatih) of the Majapahit Empire, credited with bringing the empire to its peak of glory. He is said to have delivered an oath called Sumpah Palapa, in which he vowed not to eat any food containing spices until...
Found on
http://en.wikipedia.org/wiki/Groin-vault

(from the article `building construction`) ...of stone below ground was greater than that above. To further lighten the loads, the vaults themselves were made thinner by introducing ribs at ... Roman architects discovered that two barrel vaults that intersected at right angles formed a groin vault, which, when repeated in series, could ...
Found on
http://www.britannica.com/eb/a-z/g/72

the line which two vaults, running at any angle, meet
Found on
http://www.castles-of-britain.com/glossary.htm

also known as square vault, made by intersecting two barrel vaults at right angles. The spaces created by this vault were called bay areas.
Found on
http://www.encyclo.co.uk/local/22196

A vault produced by the intersection at right angles of two barrel (tunnel) vaults. Sometimes the arches of groin vaults may be pointed instead of round.
Found on
http://www.pitt.edu/~medart/menuglossary/INDEX.HTM

a curved edge formed by two intersecting vaults.
Found on
http://www.translationdirectory.com/glossaries/glossary336.php

A vault formed by the intersection at right angles of two barrel vaults. Sometimes the arches of groin vaults may be pointed instead of round. Also see: barrel vault.
Found on
http://www.virtualani.org/glossary/index.htm
No exact match found.