Having broad hips or large buttocks. For example, I've grown too broad in the beam for these slacks. This expression originated in the 17th century and described the wideness of a ship. It began to be used for the human body only in the 1920s.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.