blue devil

(noun) a coarse prickly European weed with spikes of blue flowers; naturalized in United States. Synonyms: blueweed, blue devil, blue thistle, viper's bugloss, Echium vulgare.

(noun) the sodium salt of amobarbital that is used as a barbiturate; used as a sedative and a hypnotic. Synonyms: amobarbital sodium, blue, blue angel, blue devil, Amytal.