1. A staff officer who helps a commanding officer with administrative affairs.
2. A military officer who does office work and who is responsible for rules and punishment among the lower ranks.
3. Etymology: "a military officer who assists superior officers"; from Latin adjutantem, adjutans, adjutare, "to give help to, to help zealously, to serve"; frequentative of adjuvare past participle of adjutus, "help, assist, aid, support"; from ad-, "to" + juvare, "to help, to give strength, to support".