A Scanner Darkly, a 1977 novel by Philip K. Dick

Atrial septal defect, a medical condition affecting the heart

Adjustable-speed drive used to control electrical engine's speedness

Acute stress disorder, a psychiatric disorder

Autism spectrum disorder, a brain development disorder

Aigle - Sepey - Diablerets, a Swiss mountain railway

American School of Dubai, an educational institute located in Dubai, United Arab Emirates

Andromeda Software Development, a Greek demogroup

American Standard Companies, a global provider of air conditioning systems

Anchorage School District, the district of schools in Anchorage, Alaska

American School for the Deaf in Hartford, Connecticut

After school detention, detention held after school

Azimuthing stern drive, a drive/direction system for state of the art "tractor" tugboats

Adaptive Software Development, a software development process

Accredited Symbian Developer, a qualification for developers of software for Symbian OS

ASDF (sequence of letters), the first three letters of home row keys on a QWERTY keyboard