An AccidentalLink is a link to an article that does not exist. The AccidentalLink is presumably created accidentally, by the author inadvertantly using CamelCase or enclosing a word or phrase in square brackets. The accident is either a typo, or of assuming that an article exists when it does not, or of linking to an article one intends to contribute and then failing to contribute that article. In all cases, the result is a link that does not lead to an article.