What is the term used for a geometric transformation that involves rotating a figure without changing its size or shape?

The term that describes a geometric transformation involving the rotation of a figure without altering its size or shape is indeed commonly referred to as a "turn transformation." This transformation allows the object to maintain its dimensions and proportions while changing its orientation in space. It involves rotating the figure around a fixed point, known as the center of rotation, through a specified angle.

In contrast, reflection involves flipping a figure over a line, creating a mirror image. Translation refers to sliding a figure from one position to another without rotation or resizing. Dilation is the process of resizing a figure proportionally, which is not applicable in this context as it involves changing the figure's dimensions. Therefore, a turn transformation is the most fitting term for the described geometric action.