Meaning of posse comitatus

pos•se co•mi•ta•tus

Pronunciation: (pos'ē kom"i-tä'tus, -tā'-), [key]
  1. the body of persons that a peace officer of a county is empowered to call upon for assistance in preserving the peace, making arrests, and serving writs.
  2. a body of persons so called into service.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.