Flanker \Flank"er\, n. One who, or that which, flanks, as a skirmisher or a body of troops sent out upon the flanks of an army toguard a line of march, or a fort projecting so as to command the side of an assailing body.

They threw out flankers, and endeavored to dislodge their assailants. --W. Irwing.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Flanker \Flank"er\, v. t. [imp. & p. p. Flankered; p. pr. & vb. n. Flankering.]

[See Flank, v. t.]

1. To defend by lateral fortifications. [Obs.]

--Sir T. Herbert.

2. To attack sideways. [Obs.]

--Evelyn.

Source: Webster's Revised Unabridged Dictionary (1913)