† subˈstratorEccl.Obs.rare. [f. L. substrāt-(see substrate a.) + -or.] One of a class of penitents in the early church called substrati; = kneeler 2 a. (Cf. prostrator 2.) 1720Bingham Antiquities xviii. i. §1 The mourners or weepers, the hearers, the substrators, and the co-standers.