n 1  :  a condition that is marked by recurrent usu. unilateral severe headache often accompanied by nausea and vomiting and followed by sleep, that tends to occur in more than one member of a family, and that is of uncertain origin though attacks appear to be precipitated by dilatation of intracranial blood vessels  2  :  an episode or attack of migraine <suffers from s>  - called also sick headache  mi*grain*ous adj 
 
 Brit often   
 
Similar sounding terms:  mi·cron 
 
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