Outrigger

Noun

1. Any of various projecting beams or spars that provide support for a sailing ship's mast.
2. A long thin timber, pontoon, or other float attached parallel to a canoe or boat by projecting struts as a means of preventing tipping or capsizing.
3. An outrigger canoe or boat.
4. An iron bracket or brace for an oarlock projecting from the side of a rowing boat.
5. An extension mechanism, often retractable when not in use, on a boat, vehicle, or structure which helps to stabilize it to keep it from tipping over.