Definition(s)
Annular BOP
A device with a generally toroidal shaped steel-reinforced elastomer packing element that is hydraulically operated to close and seal around any drill pipe size or to provide full closure of the wellbore.
Source: API SPEC 16D, Specification for Control Systems for Drilling Well Control Equipment and Control Systems for Diverter Equipment, Upstream Segment, Second Edition, July 2004. Global Standards