Synonyms for Blue Devil (same or very similar meaning)
WordNet sense 1 (a coarse prickly European weed with spikes of blue flowers; naturalized in United States):
blueweed, blue thistle, Echium vulgare, viper's buglossWordNet sense 2 (the sodium salt of amobarbital that is used as a barbiturate; used as a sedative and a hypnotic):
blue, Amytal, amobarbital sodium, blue angelFrom the ODE community, based on WordNetadd/edit