ORBIT' (4 letters) The term 'planetary cycle' refers to the yearly ORBIT of a planet around its star. This is often referred to as a planet's year, and can be measured in terms of the number of days it takes for the planet to complete one full ORBIT. The crossword solutions for this term are 'year' (4 letters) and 'ORBIT' (4 letters). Together, these two words describe the yearly cycle of a planet around its star.