1. Referring to someone or something that changes or varies very often and without any understandable reason: The weather in the fall seemed to be so unstable and inconstant that Jane never knew if it was going to rain or if the sun was going to shine brightly.
2. Regarding a person who is not faithful or reliable: Grace decided never to fall in love with such a capricious man again who turned out to be inconstant and disloyal.