decan /ˈdɛkən/noun 1/di.kæn/ verb 1forms 3 noun1 •One of a collection of 36 small constellations or zodiacal subdivisions that appear heliacally at intervals of 10 days or are separated by approximately 10 degrees. decan /di.kæn/ verb1 •To remove (something, especially nuclear reactor fuel) from a can or similar protective enclosure, cladding, etc. formsdecanned · decanning · decans