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]

WordNet (r) 3.0 (2006):

Reticulum
    n 1: a small constellation in the southern hemisphere near
         Dorado and Hydrus
    2: any fine network (especially one in the body composed of
       cells or blood vessels)
    3: the second compartment of the stomach of a ruminant [syn:
       reticulum, second stomach]