1. An irrational belief that an object, action, or circumstance not logically related to a course of events influences its outcome.
a. A belief, practice, or rite irrationally maintained by ignorance of the laws of nature or by faith in magic or chance.
b. A fearful or abject state of mind resulting from such ignorance or irrationality.
Superstition – definition of superstition by the Free Online Dictionary.