The practice of sending credit card companies stuff that they don't want or need (such as coupons, or even other credit card offers that you get) using the pre-paid envelope they send you; harassing telemarketers when they call you; creating viruses that target only computers or e-mail accounts of spamers; contacting everyone and everything that might offer you something you don't want and telling them not to. Typically done as a way of entertaining yourself when you have small amounts of free time and nothing else to do. Includes the prevention in any way of any kind of advertisement.
Person A: why don't you just throw them away and ignore everything?
Person B: Because it's more fun to make an ass of myself. You should try antispaming too.