Definition of long arm:
(n) :
A pole tool used for handling things too far away to reach.
(n) :
A gun with a long barrel, such as a rifle or shotgun.
(n) :
(idiomatic) Influence; far-reaching power.
(n) :
A quilting machine that holds the fabric stationary on long rollers but allows the sewing mechanism to move around the surface of the fabric.