The Collaborative International Dictionary of English v.0.48:

Tempera \Tem"pe*ra\, n. [It.] (Paint.)
   A mode or process of painting; distemper.
   [1913 Webster]

   Note: The term is applied especially to early Italian
         painting, common vehicles of which were yolk of egg,
         yolk and white of egg mixed together, the white juice
         of the fig tree, and the like.
         [1913 Webster]

WordNet (r) 3.0 (2006):

tempera
    n 1: pigment mixed with water-soluble glutinous materials such
         as size and egg yolk [syn: tempera, poster paint,
         poster color, poster colour]