A chemical element and precious metal, symbol Ag, atomic number 47.
In the World of Darkness, silver is important inasmuch as garou have a special vulnerability to it. Weapons made of silver inflict aggravated damage upon them, and the mere sight of silver has been known to make a garou enter frenzy.
Lupus and homid garou avoid aggravated damage from silver when in their birth form, but even so, they tend to avoid the metal where possible. There are some exceptions, e.g. klaives are usually made of silver. Metis suffer aggravated damage from silver in all forms.
It has been known for the enemies of garou to make silver weapons specifically to use in fights against them. Silver bullets are, thankfully, not easy to manufacture or come by, although not unknown.