Longman Dictionary of Contemporary English
war widow
noun
EXAMPLES FROM CORPUS
▪ She was a war widow and worked round the clock in her efforts to bring up a young family by herself.
Wiktionary
war widow
n. 1 The wife of a man in the armed forces killed in a war (and sometimes in other military action). 2 (context by extension English) A woman whose husband has been killed in any conflict.
WordNet
war widow
n. a woman whose husband has died in war