Sierra Madre Oc·ci·den·tal 
(ŏk′sĭ-dĕntəl, ōk′sē-dĕn-täl)
(ŏk′sĭ-dĕntəl, ōk′sē-dĕn-täl) A mountain range of northwest Mexico running parallel to the Pacific coastline and adjoining the Mexican plateau. It extends for about 1,610 km (1,000 mi) southward from the border of Arizona.