Superstition is one of those confusing words that have a rather clear definition, but that in practice people use it in a quite different way. It has a slightly negative connotation and, therefore, people rarely identify with the term even if they believe in astrology, homeopathy, crystal healing, etc. In practice, for something to be called superstition, besides the formal definition, it has to be a small, isolated belief that is outside the framework of any big, organized religion, or even a loose set of beliefs that is popular enough like the new age movement for example. If you believe black cats bring bad luck, you’ll be called superstitious. If you believe Jesus walked over water, you’ll be called religious. If you believe in auras, chakras or other new age stuff, you’ll be called “spiritual” or something similar.

Technically, however, all of these fit the definition of superstition perfectly. Believing in God or immortal souls, a core belief in most religions, is by definition superstition. They are all beliefs “connected with old ideas about magic” and with “no rational substance”.