1. [n]  the activity of going around or through an area at regular intervals for security purposes
2. [n]  a detachment used for security or reconnaissance
3. [n]  a group that goes through a region at regular intervals for the purpose of security
4. [v]  maintain the security of by carrying out a control

Patrol
This poetic picture book explores the feelings of an American soldier fighting in the Vietnam War. Illustrated with mixed-media collages.

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1. \Pa*trol"\, n.
   See {Boy Scout}.
   

2. \Pa*trol"\, v. i. [imp. & p. p. {Patrolled}; p. pr. & vb.
   n. {Patrolling}.] [F. patrouiller, O. & Prov. F. patrouiller
   to paddle, paw about, patrol, fr. patte a paw; cf. D. poot
   paw, G. pfote, and E. pat, v.]
   To go the rounds along a chain of sentinels; to traverse a
   police district or beat.
   

3. \Pa*trol"\, v.
   t To go the rounds of, as a sentry, guard, or policeman; as,
   to patrol a frontier; to patrol a beat.
   

4. \Pa*trol"\, n. [F. patrouille, OF. patouille. See
   {Patrol}, v. i.]
   1. (Mil.)
      (a) 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.
      (b) A movement, by a small body of troops beyond the line
          of outposts, to explore the country and gain
          intelligence of the enemy's whereabouts.
      (c) The guard or men who go the rounds for observation; a
          detachment whose duty it is to patrol.
   2. Any perambulation of a particular line or district to
      guard it; also, the men thus guarding; as, a customs
      patrol; a fire patrol.
            In France there is an army of patrols to secure her
            fiscal regulations.                   --A. Hamilton.