Source : Webster's Revised Unabridged Dictionary (1913)

Sumerian \Su*me"ri*an\, a. [Written also {Sumirian}.]
   Of or pertaining to the region of lower Babylonia, which was
   anciently called Sumer, or its inhabitants or their language.

Sumerian \Su*me"ri*an\, n. [Written also {Sumirian}.]
   A native of lower Babylonia, anciently called Sumer.

Source : WordNet®

Sumerian
     adj : of or relating to ancient Sumer or its inhabitants
     n : a member of a people who inhabited ancient Sumer