What is Argent?

Legal Definition
In heraldry, argent /ˈɑːrənt/ is the tincture of silver, and belongs to the class of light tinctures, called "metals". It is very frequently depicted as white and usually considered interchangeable with it. In engravings and line drawings, regions to be tinctured argent are either left blank or indicated with the abbreviation ar. in them.

The name derives from Latin argentum, translated as "silver" or "white metal." The word argent had the same meaning in Old French blazon, from which it passed into the English language.

In some historical depictions of coats of arms, a kind of silver leaf was applied to those parts of the device that were argent. Over time, the silver content of these depictions has tarnished and darkened. As a result, it can sometimes be difficult to distinguish regions that were intended as argent from those that were sable. This leaves a false impression that the rule of tincture has been violated in cases where, when applied next to a dark colour, argent now appears to be sable due to tarnish.
-- Wikipedia
Legal Definition
In heraldry. Silver.
-- Black's Law Dictionary