D4
From the White Wolf Wiki, the most complete White Wolf reference
A d4 — also called a four-sided die, a caltrop or, less commonly, a tetrahedron — is one of several standard polyhedral dice used in gaming. Each type is generally identified by the use of the letter "d" (for "die" or "dice") and the number of sides the die features. Multiple dice are connotated by an additional number prefixing the D. So rolling five four-sided dice would be noted by writing 5d4.
The d4 is infrequently used, but is one of the standard dice in the d20/OGL system.
