The slippery slope fallacy is a form of negative reasoning from consequences, in which a proposed action is incorrectly presumed to lead to a negative outcome. An example can be the case of someone (person 1) wanting to engage in a behaviour that another person (person 2) disapproves of. Person 1 might warn against this behaviour, and argue that it may lead to other, similar behaviours, despite the fact that there is no basis for assuming that the other behaviours will automatically follow.
Source:
Tindale, C. W. (2007). “Correlation and Cause”. In Fallacies and Argument Appraisal 