lumbar triangle

n.
  1. An area in the posterior abdominal wall, the site of occasional herniation, bounded by the edges of the latissimus dorsi and external oblique muscles and the iliac crest.Petit's lumbar triangle
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.