Source : Webster's Revised Unabridged Dictionary (1913)

Hemicrania \Hem`i*cra"ni*a\, n. [L.: cf. F. h['e]micr[^a]nie.
   See {Cranium}, and {Megrim}.] (Med.)
   A pain that affects only one side of the head.

Source : WordNet®

hemicrania
     n : a severe recurring vascular headache; occurs more frequently
         in women than men [syn: {migraine}, {megrim}, {sick
         headache}]