Definition of rocker-bottom in US English:

rocker-bottom

noun

  • 1A convexly curved underside, as of some types of rail truck, boat, etc.; compare sense 9b.

  • 2Medicineattributive designating a foot characterized by convexity of the sole or weight-bearing surface, and the deformity of having such a foot.

Origin

Mid 19th century; earliest use found in The Mechanics' Magazine.