Source : Webster's Revised Unabridged Dictionary (1913)

Perineum \Per`i*ne"um\, n. [NL., fr. Gr. ?, ?.] (Anat.)
   The region which is included within the outlet of the pelvis,
   and is traversed by the urinogenital canal and the rectum.

Source : WordNet®

perineum
     n : the general region between the anus and the genital organs
     [also: {perinea} (pl)]