Pseudoscience is knowledge that has the appearance of science but it is not, especially fraudulent knowledge that claims to use the scientific method or similar to support such knowledge.
Wikipedia (2010) defines "pseudoscience" as a claim, belief, or practice which is presented as scientific, but which does not adhere to a valid scientific methodology, lacks supporting evidence or plausibility, cannot be reliably tested, or otherwise lacks scientific status. According to this definition, thus, pseudoscience includes knowledge approaching scientific knowledge but that either was considered scientific but has since being discredited by the scientific method and other theories, or has not being subjected to the scientific method as yet. An example of the first case came since the acceptance of Einstein's Theory of relativity, which downgraded some previous scientific theories and experiments from scientific and onto the realm of pseudoscience. Examples of the second case are theories and hypotheses that have not yet being put to scientific scrutiny, like Reason's (1990) model of accident causation, or that have been tested only partially or circumstantially (which is the case with much social science research).
Notwithstanding this, pseudoscience is mostly used for referring to "fraudulent science", and this use may thus conflict with the earlier two considerations. In this case, it may be more advantageous to use the concept of pseudoscience for referring to "fraudulent science" and, perhaps, "bad science", while discarded scientific knowledge and unproved theoretical models may be considered as historical science and either protoscience or as technology, respectively.