Noun
English Wikipedia has an article on:truss rodWikipedia
truss rod (plural truss rods)
A steel rod that stabilises the neck of a guitar
Turning the truss rod clockwise tightens it, counteracting the tension of the strings and straightening the neck or creating a backward bow. Source: Internet
Turning the truss rod counter-clockwise loosens it, allowing string tension to act on the neck and creating a forward bow. Source: Internet
Some instruments have a filler strip running down the length and behind the neck, used for strength or to fill the cavity through which the truss rod was installed in the neck. Source: Internet
Some truss rod systems, called double action truss systems, tighten both ways, pushing the neck both forward and backward (standard truss rods can only release to a point beyond which the neck is no longer compressed and pulled backward). Source: Internet
The truss rod is a metal rod that runs along the inside of the neck. Source: Internet