Ocurring in spells is a term used to describe a certain type of behavior or action that is repeated in a short period of time. The two crossword solutions for this term are SPASMODIC and FITFUL. SPASMODIC is an adjective that describes something that is sudden, irregular, and uncontrolled. FITFUL is an adjective that describes something that is intermittent, irregular, and unpredictable. Both words can be used to describe a behavior or action that occurs in a short period of time.