tetradic

[Eng. tetrad; -ic.] Of or pertaining to a tetrad; tetratomic. tět-ra-dites, s. pl. [ Gr.tetrad is tai =young people who feasted on the fourth day of the month.] 1. Gr. Antiq .: Persons who were born on the fourth day of the month, which was reputed to be lucky. 2. Church History (in this sense probably directly from Gr. tetra- , in comp.=four): (1) Heretics who fasted at Easter, as on Wednesday. (2) Certain ancient sects who held the number four in special reverence, to the extent of supposing the existence of a fourth person added to the Trinity.