Rigid motion with reflected repetition along a line.

A two-step isometry that is a composition of a translation and a reflection in a line that is parallel to the translation vector (Lesson 8.1).

In geometry, a glide reflection is a type of isometry of the Euclidean plane: the combination of a reflection in a line and a translation along that line. Reversing the order of combining gives the same result. Depending on context, we may consider a reflection a special case, where the translation vector is the zero vector.