Sentence:  They are the standing army, and the militia, jailers, constables, <WSD>"posse comitatus</WSD>", etc. 
Meaning of the word marked with <WSD> tags:  The able-bodied men over 15 in a given county who can be summoned by the sheriff to help keep the peace, or arrest a felon; also a group of men so gathered. (from early 17th c.)