Onuf's nucleus

[ŏnəfs]
n.
  1. A nucleus of small somatic motor neurons that are located in the ventral horn of the spinal cord at the level of the second sacral vertebra and innervate the vesicorectal sphincters.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.