This is a necessary word, defined by Wikipedia as:
... misinformation packaged to look like fact. The claims of counterknowledge, such as those made by pseudohistorians and pseudoscientists, can be identified because there are facts to contradict them, or because there is no evidence to support them. Systems of counterknowledge can appear sophisticated, even internally consistent, but ultimately they are 'systems of counterfactual belief'.
And there's a website devoted to it, by Damian Thompson, the editor-in-chief of the Catholic Herald, where he looks at such claims as "Muslims discovered America before Columbus" (wasn't it the Chinese?). He has another blog at the Telegraph called Holy Smoke.