The extreme left or right of a military formation. The following is an extract:

Flank attack (Mil.), an attack upon the side of an army or body of troops, distinguished from one upon its front or rear.

Flank company (Mil.), a certain number of troops drawn up on the right or left of a battalion; usually grenadiers, light infantry, or riflemen.

Flank defense (Fort.), protection of a work against undue exposure to an enemy's direct fire, by means of the fire from other works, sweeping the ground in its front.

Flank en potence (Mil.), any part of the right or left wing formed at a projecting angle with the line.

Flank files, the first men on the right, and the last on the left, of a company, battalion, etc.

Flank march, a march made parallel or obliquely to an enemy's position, in order to turn it or to attack him on the flank.

Flank movement, a change of march by an army, or portion of one, in order to turn one or both wings of the enemy, or to take up a new position.

Flanks of a frontier, salient points in a national boundary, strengthened to protect the frontier against hostile incursion.

Flank patrol, detachments acting independently of the column of an army, but patrolling along its flanks, to secure it against surprise and to observe the movements of the enemy.
An out-flanking manoeuvre.
by Kung-Fu Jesus May 03, 2004
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A sexual gropage of the calf.
Ian walked up behind Jacob and flanked him suddenly. Jacob felt violated later on and showered for three hours straight.
by elbowlicker March 29, 2010
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To pwn someone, either figuratively or literally, by bludgeoning them upside the head with your gigantic cock.
Buzzed Bunny says to flank the fuckton of ninjas that show up when you're fucking your girlfriend in the ass.
by AceMaster2000 May 05, 2006
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A prank move pulled by two conspirators in a men's restroom that does not have barriers between the urinals. Ignoring proper urinal etiquette, the two prankers come up on either side of a lone pisser and angle 45 degrees so as to piss into the same urinal as the man being pranked. Usually complemented with a conversation across the middle man.
Hey, this is a perfect time to flank him, let's go.
by kidnutrageous June 02, 2006
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The word flank is used as a substitute to most key words in a sentence, especially swear words
What the 'flank'?

You get flanked right up yer flank hole mate
by baz January 19, 2005
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