what MIA means
adjective. 1  acronym for missing in action. 2  Though the term has military origins, it is also used to simply imply that a person hasn't been seen in some period of time. 3  She's been MIA since the bar last night. 4  See more words with the same meaning: acronyms (list of) . She's been MIA since the bar last night. 2  See more words with the same meaning: acronyms (list of) . 3  See more words with the same meaning: lost, missing, misplaced. 4  See more words with the same meaning: military (related to) .