The Collaborative International Dictionary of English v.0.48:

absorbent \ab*sorb"ent\ ([a^]b*s[^o]rb"ent), a. [L. absorbens,
   p. pr. of absorbere.]
   Absorbing; swallowing; absorptive.
   [1913 Webster]

   Absorbent ground (Paint.), a ground prepared for a picture,
      chiefly with distemper, or water colors, by which the oil
      is absorbed, and a brilliancy is imparted to the colors.
      [1913 Webster]