The Collaborative International Dictionary of English v.0.48:
corncockle \corncockle\ n. a European annual (Agrostemma githago) having large trumpet-shaped reddish-purple flowers and poisonous seed; a common weed in grainfields and beside roadways; naturalized in America. Syn: corn cockle, corn-cockle, corn campion, crown-of-the-field, Agrostemma githago. [WordNet 1.5]