| Acronym | Sense | Language | Topics |
|---|---|---|---|
| AO | Acta Orientalia | In Latin | → Serial publications, periodicals → Language, linguistics, literature → Geography, biography, history |
| AO | Aula Orientalis | In Latin | → Language, linguistics, literature → Geography, biography, history |
| AO | Analog Output | In English | |
| AO | Announcement of Opportunity | In English | |
| AO | Apostolic Oblates | In English | → Roman catholic church |
| AO | Action Ouvrière | In French | → Political parties and movements → Encyclopaedias, reference works |
| AO | Alternative Officing | In English | → Labour, labour economics |