What is the muscle (line) that form between the eyes (over the nose)?

The Procerus muscle: The two muscles so named, close together on each side of the midline, occupy the bridge of the nose and are closely associated with the corrugator supercilii. It increases the prominence of the eyebrows as a protection when the eyes are exposed to bright light. From the point of view of facial expression it is the muscle of "aggression" or "menace". Associated with other muscles it expresses pain.

Procerus/corrugators: The horizontal line between the eyebrows is formed by contraction of the procerus muscle. The two vertical lines between the eyebrows is formed by contraction of the corrugators. Together this area (procerus/corrugators) is called the glabella. If these lines are present at rest, treatment includes observation or they can be softened with neuromodulators (botox) to weaken those muscles.