Obsessive-compulsive disorder, a psychological disorder

Object collision detection

Osteochondritis dissecans, a painful joint condition in humans and animals

On-chip debugging

Ordo Carmelitarum Discalceatorum (Discalced Carmelite Order)

Office of Community Development, a part of the U.S. Department of Agriculture's rural development activities

Okanogan Conservation District

Oxford Classical Dictionary

Ortho-Clinical Diagnostics

Office of Civilian Defense, a World War II-era U.S. government agency

Octavian County Day School, a school attended by characters of Lisi Harrison's The Clique (novel) books