Medical Definition of SUBOCCIPITAL. 1. : situated or performed below the occipital bone.2. : situated or performed below the occipital lobe of the brain.3 ENTRIES FOUND:1  suboccipital (adjective).edical Definition of SUBOCCIPITAL. 1. : situated or performed below the occipital bone. 2. : situated or performed below the occipital lobe of the brain. 3 ENTRIES FOUND: 1  suboccipital (adjective).