trĭbŭlus
i, m.
I.
an instrument resting on three of its iron prongs, while a fourth projected upward, thrown on the ground to impede an enemy's cavalry, a caltrop.
I.
Lit.: tribulos abjecerunt, Veg. Mil. 3, 24.—
II.
Transf., from its resemblance in form.
A.
A kind of thorn or thistle, land-caltrops: Tribulus terrestris, Linn.; Verg. G. 1, 153; Ov. M. 13, 803; Plin. 21, 15, 54, § 91: spinae et tribuli, Vulg. Gen. 3, 18.—
B.
A kind of water-plant bearing a prickly nut of a triangular form, water - chestnut, water - caltrops: Trapa natans, Linn.; Plin. 21, 16, 58, § 98.