innermost intercostal muscle

[ĭnər-mōst]
n.
  1. A layer of muscle parallel to the internal intercostal muscle but separated from it by the intercostal vessels and nerves.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.