triverbial

from The Century Dictionary.

• Of three words: applied to certain days in the Roman calendar which were juridical, or days appointed to the pretor for deciding causes: so named from the three characteristic words of his office, do, dico, addico. They were also called dies fasti.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (Rom. Antiq.) Pertaining to, or designating, certain days allowed to the pretor for hearing causes, when be might speak the three characteristic words of his office, do, dico, addico. They were called dies fasti.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective historical Relating to, or designating, certain days allowed to the pretor for hearing causes, when he might speak the three characteristic words of his office: "do, dico, addico".