Double-barreled shotgun

A view of the break-action of a typical side-by-side (SxS) double-barreled shotgun, with the Anson & Deeley boxlock action open and the extractor visible. The lever and the safety catch can also be clearly seen.
A view of the break-action of a typical over-and-under (O/U) double-barreled shotgun, with action open and the ejectors visible
Two .410 shells being loaded into a side-by-side, double-barrel shotgun

A double-barreled shotgun, also known as a double shotgun, is a break-action shotgun with two parallel barrels, allowing two single shots that can be fired simultaneously or sequentially in quick succession.