To refuse to buy a product or service from a company or person, usually on the grounds that there is something morally questionable about the vendor or the way that the product is made.

Boycotting is most effective when done on a large scale with huge groups of people, so that sales actually go down significantly, and the company starts to reconsider their practices. Some people, though, try to be noble by personally boycotting huge corporations, because they have unfair business practices, or do tests on animals, or are involved in foolish lawsuits. No matter how often you tell them that they're not going to make any kind of scratch in the company's income, and are only cheating themselves out of more reliable products and services, they've already gotten themselves on a big headtrip where they think that their own purchasing practices matter at all.

Most of the time, this kind of behavior can be blown off, as it doesn't really have much effect on others. It gets highly annoying, however, when a group of friends is forced to drive around for hours trying to find something to do, just because one person says "No, we can't go see that movie that the rest of you want to watch, because I'm boycotting the MPAA."