The Collaborative International Dictionary of English v.0.48:

Rhizopod \Rhiz"o*pod\, n. (Zool.)
   One of the Rhizopoda.
   [1913 Webster]

   Note: The rhizopods belonging to the Radiolaria and
         Foraminifera have been of great geological importance,
         especially in the Cretaceous and Tertiary periods.
         Chalk is mostly made from the shells of Foraminifera.
         The nummulites are the principal ingredient of a
         limestone which is of great extent in Europe and Asia,
         and is the material of which some of the pyramids of
         Egypt are made. The shells are abundant in deepsea mud,
         and are mostly minute, seldom larger than a small grain
         of sand, except in the case of the nummulities, which
         are sometimes an inch in diameter.
         [1913 Webster]

WordNet (r) 3.0 (2006):

rhizopod
    n 1: protozoa characterized by a pseudopod [syn: rhizopod,
         rhizopodan]