caltrop
(noun)
noun
1. tropical annual procumbent poisonous subshrub having fruit that splits into five spiny nutlets; serious pasture weed
Definition categories: plant, subshrub, suffrutex
2. a plant of the genus Trapa bearing spiny four-pronged edible nutlike fruits
Definition categories: plant, hydrophyte
3. Mediterranean annual or biennial herb having pinkish to purple flowers surrounded by spine-tipped scales; naturalized in America