Annual or perennial herbs sometimes with a woody base. Leaves opposite, paripinnate, one of each pair usually larger than the other. Leaflets opposite, entire, slightly asymmetrical. Flowers solitary, axillary. Petals yellow. Ovary 5-lobed, densely stiffly hairy. Fruit breaking up into 5 cocci, each coccus tuberculate on the back, spiny, 1-5-seeded.
Tribulus is also a derivative Roman era (Latin) name for the weapon known in English today as the caltrop, which bears strong resemblances with the plant today named Latin: Tribulus terrestris or puncture vine.
Tribulus is a genus of plants found in many warm regions. The best-known member is T. terrestris (puncture vine), a widespread weed and also the source of a dietary supplement. T. terrestris has been said to raise natural testosterone levels if taken as a supplement. There have been no studies that show a direct correlation between the use of tribulus and an increase in natural testosterone.
Tribulus species are perennial, but some grow as annuals in colder climates. The leaves are opposite and compound. The flowers are perfect (hermaphroditic) and insect-pollinated, with fivefold symmetry. The ovary is divided into locules that are in turn divided by "false septa" (the latter distinguish Tribulus from other members of its family).
Some species are cultivated as ornamental plants in warm regions. Some, notably T. cistoides, T. longipetalus, T. terrestris, and T. zeyheri, are considered weeds. Tribulus omanense is the national flower of Dubai. Thirteen species of Tribulus are accepted by Kew, but there are many still unresolved and needing further study. 
^Battle of Alesia (Julius Caesar's conquest of Gaul in 52 BC)), Battlefield Detectives program, (2006), rebroadcast: 2008-09-08 on History Channel International (13:00–14:00 hrs EDST); Note: No mention of name caltrop at all, but illustrated and given as battle key to defend Roman lines of circumvallation per recent digs evidence.