Definitions of keel:

• noun:   one of the main longitudinal beams (or plates) of the hull of a vessel; can extend vertically into the water to provide lateral stability
• noun:   the median ridge on the breastbone of birds that fly
• verb:   walk as if unable to control one's movements
• name:  A surname (rare: 1 in 33333 families; popularity rank in the U.S.: #3630)