The Collaborative International Dictionary of English v.0.48:

Reticulum \Re*tic"u*lum\, n.;pl. Reticula. [L. dim. of rete a
   net.] (Anat.)
   (a) The second stomach of ruminants, in which folds of the
       mucous membrane form hexagonal cells; -- also called the
       honeycomb stomach.
   (b) The neuroglia.
       [1913 Webster]