patrol
n//pæʈɾol//patrull
(military) A going of the rounds along the chain of sentinels and between the posts, by a guard, usually consisting of three or four men, to insure greater security from attacks on the outposts.
(military) The guards who go the rounds for observation; a detachment whose duty it is to patrol.
Any perambulation of a particular line or district to guard it; also, the people thus guarding.