The Collaborative International Dictionary of English v.0.48:

metate \me*ta"te\ (m[asl]*t[aum]"t[asl]), n. [Sp., fr. Mex.
   metlatl.]
   A flat or somewhat hollowed stone upon which grain or other
   food is ground, by means of a smaller stone or pestle.
   [Southwestern U. S. & Sp. Amer.]
   [Webster 1913 Suppl.]