triangularis

noun

tri·​an·​gu·​la·​ris trī-ˌaŋ-gyə-ˈlar-əs 

plural triangulares -ˈlar-ˌēz 

1

: a flat triangular muscle that extends from the base of the mandible to the angle formed by the joining of the upper and lower lips and that acts to depress this angle

2

: triquetral bone