A superstition is any belief or practice considered by non-practitioners to be irrational or supernatural, attributed to fate or magic, perceived supernatural influence, or fear of that which is unknown. It is commonly applied to beliefs and practices surrounding luck, amulets, astrology, fortune telling, spirits, and certain paranormal entities, particularly the belief that future events can be foretold by specific (apparently) unrelated prior events.

Also, the word superstition is often used to refer to a religion not practiced by the majority of a given society regardless of whether the prevailing religion contains alleged superstitions.

More Info: en.wikipedia.org