Deviating off course is a term used to describe when something is not following its intended path or direction. It can be caused by a variety of factors, such as an unexpected change in the environment or an error in navigation. Two words that can be used to describe this phenomenon are 'ERRATIC' and 'yawing'. ERRATIC means unpredictable or inconsistent in behavior or direction, while yawing refers to a side-to-side movement or turning away from a straight line.