Either of the two large flat triangular muscles that run from the back of the neck and cover each shoulder. They help to move the shoulder blades and draw the head backward. The trapezius muscle has several other functions:
to move the shoulder blade in toward the spine, to rotate the shoulder blade so that the topmost part of the upper arm faces up, to move the shoulder blade up and down, to bring the head and neck in a backward direction, to rotate and side bend the neck and to assist in breathing. A common exercise for the Trapezius muscle is the seated row.