The Collaborative International Dictionary of English v.0.48:

Fresco \Fres"co\, n.; pl. Frescoes or Frescos. [It., fr.
   fresco fresh; of German origin. See Fresh, a.]
   1. A cool, refreshing state of the air; duskiness; coolness;
      shade. [R.] --Prior.
      [1913 Webster]

   2. (Fine Arts)
      (a) The art of painting on freshly spread plaster, before
          it dries.
      (b) In modern parlance, incorrectly applied to painting on
          plaster in any manner.
      (c) A painting on plaster in either of senses
      a and
      b .
        [1913 Webster]

   al fresco in the open air; out of doors; outdoors; as, to
      dine al fresco.
      [PJC]