Either of two beams or fins fastened lengthwise along the outside of a ship's bilge to inhibit heavy rolling.
(plural bilge keels)
- (nautical) a strake, or small keel or blister, running along much of the length of the hull. It is used to reduce the hull's tendency to roll. They are typically fitted one on each side, low down on the side of the hull, so as not to increase the draft of the vessel. In battleships they were often quite large and used as part of the torpedo protection system.