
1) Military installation 2) Place for a dry run 3) Weapons-testing area
Found on
https://www.crosswordclues.com/clue/proving-ground

A proving ground is the US name for a military installation or reservation where weapons or other military technology are experimented with or are tested, or where military tactics are tested. The usual British term is training area. While these types of facilities are usually military or government establishments, some civilian industries have th...
Found on
http://en.wikipedia.org/wiki/Proving_ground

area used for testing devices and equipment, usually, though not always, military. Testing, in general, has for its purpose the determination of the ...
Found on
http://www.britannica.com/eb/a-z/p/125

[
n] - a workplace for testing new equipment or ideas
Found on
http://www.webdictionary.co.uk/definition.php?query=proving%20ground
noun a workplace for testing new equipment or ideas
Found on
https://www.encyclo.co.uk/local/20974

any place, context, or area for testing something, as a piece of scientific equipment, a theory, etc.
Found on
https://www.infoplease.com/dictionary/proving-ground
No exact match found.