platysma

noun

pla·​tys·​ma plə-ˈtiz-mə 

plural platysmata -mət-ə  also platysmas

: a broad thin layer of muscle that is situated on each side of the neck immediately under the superficial fascia belonging to the group of facial muscles, that is innervated by the facial nerve, and that draws the lower lip and the corner of the mouth to the side and down and when moved forcefully expands the neck and draws its skin upward

platysmal

-məl 

adjective