Substo, substas, substiti, substitum, pe. cor. substâre. Teren. To sustaine, or avine constantly.
Lewis and Short: Latin dictionary
sub-sto, āre, v. n.I.To stand or be under or among, to be present (very rare; not in Cic.): si pure substante non rumpuntur hi tumores, Cels. 6, 10 med.: nullo dolore substante, id. 2, 7 med.; 2, 12, 2.— II.To stand firm, hold out, = subsisto: metuo, ut substet hospes, Ter. And. 5, 4, 11.