VAO stands for View All Online (online document browsing; KnowledgeTree project)
VAO stands for Vertex Array Object (computing)
VAO stands for Vienna Art Orchestra (Austria)
VAO stands for Voting Assistance Officer
VAO stands for Veterans and Agent Orange (Institute of Medicine; Washington, DC)
VAO stands for Village Administrative Officer (India)
VAO stands for Voortgezette Academische Opleiding (Dutch: Continuing Academic Education)
VAO stands for Vision Assistée par Ordinateur (French: Computer-Aided Vision; artificial intelligence)
VAO stands for Voluntary Action Orkney (Scotland, UK)
VAO stands for Virtual Astronomical Observatory (Associated Universities, Inc.)
VAO stands for Volunteer Ambulance Officer