WordNet (r) 3.0 (2006):

blue devil
    n 1: a coarse prickly European weed with spikes of blue flowers;
         naturalized in United States [syn: blueweed, blue
         devil, blue thistle, viper's bugloss, Echium
         vulgare]
    2: the sodium salt of amobarbital that is used as a barbiturate;
       used as a sedative and a hypnotic [syn: amobarbital sodium,
       blue, blue angel, blue devil, Amytal]