pelvic plane of greatest dimensions

n.
  1. The plane extending from the middle of the posterior surface of the pubic symphysis to the junction of the second and third sacral vertebrae, passing laterally through the ischial bones over the middle of the acetabulum.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.