From Longman Dictionary of Contemporary Englishmissing in actionmissing in actiona soldier who is missing in action has not returned after a battle and their body has not been found → missing
Examples from the Corpus
missing in action• Discussion covered procedures for avoiding accidental clashes, disclosing the location of mines, and exchanging information about those missing in action.• Kip was never finally listed as killed or missing in action.• Woodson has been missing in action completely since tearing up his knee in the season opener.• For the past decade, Gabe Kaplan has been missing in action from the entertainment trenches.• For investors, the realization that inflation remains missing in action is a positive. 