Radial motion is a term commonly used to describe the movement of an object that follows a straight line from a center point. However, there are several synonyms that can be used to describe radial motion, such as linear motion, in which an object moves in a straight line from one point to another. Other synonyms for radial motion include straight-line motion, direct motion, and rectilinear motion. Another alternate term is direct movement, which suggests a forward or straight movement. Additionally, radial motion can be described as rectilinear, meaning that it moves in a straight line with constant speed. Overall, these synonyms can provide more variety and descriptive language when talking about objects moving in straight lines.