The term "wad" can have multiple meanings depending on its context.
In a general sense, it refers to a small mass or lump of something, often used in phrases such as "a wad of cash," which means a large sum of money held together in the form of bills.
However, if we are talking about guns and ammunition, "wad" can refer to the paper or plastic material that holds several pellets or BBs together inside a shotgun shell.
In addition, "wad" could also be used as a verb meaning to stuff something into a small space, such as putting wads of gum into your mouth.