theatre of operations is a noun meaning "a region in which active military operations are in progress". It carries one recorded sense.
a region in which active military operations are in progress
“the army was in the field awaiting action”
“he served in the Vietnam theater for three years”
military
Definitions, synonyms and semantic relations for theatre of operations come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.