Definitions for "Trapezius"
either of two flat triangular muscles of the shoulder and upper back that are involved in moving the shoulders and arms
large, trapezoidal-shaped muscle stretching from the superior, dorsal midline to the shoulder; lifts the shoulder
Greek trapezion = a trapezium - a quadrilateral with 2 sides parallel; hence, trapezius muscle, the diamond-shape of both trapezii muscles together.