1) Buffalo-nut of China 2) Dicot genus 3) Genus trapa 4) Magnoliopsid genus 5) Water chestnut genus 
Trapa is a genus of tropical, aquatic herbaceous plants (the Water Caltrops) of the family Onagrariaceae. They bear solitary flowers, followed by one celled bony beaked fruits. The submerged leaves are pinnatipartiate, with filiform segments, the floating leaves being rhomboidal. Their nuts are often consumed as food (as in the case of Trapa Natans...
[n] - small genus of Eurasian aquatic perennial herbs: water chestnut
genus Trapa noun small genus of Eurasian aquatic perennial herbs: water chestnut