Definitions
1.nounA 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.
2.nounA movement, by a small body of troops beyond the line of outposts, to explore the country and gain intelligence of the enemy's whereabouts.
3.nounThe guards who go the rounds for observation; a detachment whose duty it is to patrol.
4.nounAny perambulation of a particular line or district to guard it; also, the people thus guarding."a customs patrol"
5.nounA unit of a troop, usually defined by certain ranks or age groups within the troop.