(Fr. patrouiller, connected with patte, foot), a verb meaning to move up and down or traverse a specified "round" or "beat" in a district in a town, camp or other place, or on a stretch of water on a river or sea, for the purpose of watching and protecting the same, or for reconnoitring the numbers or positions of an enemy. As a substantive the term is used of the detachment of troops or police employed.