Lewis & Short

expressĭo, ōnis, f. [exprimo] (postAug.), a pressing or squeezing out.

  1. I. In gen.: mellis, Pall. Jun. 7, 3: spiritus, Vitr. 9, 9.
  2. II. In partic.
    1. A. In mechanics, a forcing apparatus to raise water, Vitr. 1, 1; 8, 7; cf. 2. expressus.
    2. B. In architect., a projection, i. e. a fillet, listel, Vitr. 4, 4 fin.
    3. C. Of lang., vividness: summā expressione describere, Ambros. de Cain et Abel, 1, 2, 9.