The Collaborative International Dictionary of English v.0.48:

Porridge \Por"ridge\, n. [Probably corrupted fr. pottage; perh.
   influenced by OE. porree a kind of pottage, OF. porr['e]e,
   fr. L. porrum, porrus, leek. See Pottage, and cf.
   Porringer.]
   A food made by boiling some leguminous or farinaceous
   substance, or the meal of it, in water or in milk, making of
   broth or thin pudding; as, barley porridge, milk porridge,
   bean porridge, etc.
   [1913 Webster]

WordNet (r) 3.0 (2006):

porridge
    n 1: soft food made by boiling oatmeal or other meal or legumes
         in water or milk until thick

Moby Thesaurus II by Grady Ward, 1.0:

90 Moby Thesaurus words for "porridge":
   albumen, batter, bonnyclabber, breakfast food, butter, cataplasm,
   cereal, clabber, cornflakes, cornstarch, cream, crush, curd,
   dental pulp, dough, dry cereal, egg white, farina, frumenty, gaum,
   gel, gelatin, glair, glop, glue, gluten, goo, gook, goop, grits,
   gruel, gumbo, gunk, hasty pudding, hominy grits, hot cereal, jam,
   jell, jelly, kasha, loblolly, mash, millet, molasses, mucilage,
   mucus, mush, oatmeal, pap, paper pulp, paste, pasticcio, pastiche,
   patchwork, pith, plaster, potpourri, poultice, pudding,
   puffed rice, puffed wheat, pulp, pulp lead, pulpwood, puree, putty,
   rag pulp, rob, rolled oats, salad, salmagundi, sauce, semifluid,
   semiliquid, size, smash, smorgasbord, soup, sponge, squash, starch,
   stew, sticky mess, sulfate pulp, sulfite pulp, syrup, treacle,
   wheatflakes, white lead, wood pulp