Lewis & Short

pressĭo, ōnis, f. [premo].

  1. I. Lit., a pressing, pressing down, pressure (only in Vitruvius): pressio cacuminis, Vitr. 10, 8.
  2. II. Transf., the prop or fulcrum under a lever while the burden is raised, Caes. B. C. 2, 9, 6: pressio, quod Graeci ὑπομόχλιον appellant, Vitr. 10, 8.