A3D stands for Aureal 3-Dimensional (computer sound chip; Aureal Semiconductor, Inc.) A3D stands for Advanced 3-Dimensional Audio
A3N stands for Alien 3aba6 Network
A4AA stands for Area 4 Agency on Aging
A3CR2 stands for American Alliance of Academic Chief Residents in Radiology
A4CM stands for Association for Civic Media
A4D stands for Appetite 4 Destruction
A431 stands for human epidermoid carcinoma cells
A51 stands for Area 51
A7F stands for Avenged Sevenfold (band)
A7r5 stands for Smooth Muscle Cell Line