The Collaborative International Dictionary of English v.0.48:

Parapodium \Par`a*po"di*um\, n.; pl. Parapodia. [NL., fr. Gr.
   para` beside + ?, dim. of ? foot.] (Zool.)
   One of the lateral appendages of an annelid; -- called also
   foot tubercle.
   [1913 Webster]

   Note: They may serve for locomotion, respiration, and
         sensation, and often contain spines or set[ae]. When
         well developed, a dorsal part, or notopodium, and a
         ventral part, or neuropodium, are distinguished.
         [1913 Webster]

WordNet (r) 3.0 (2006):

parapodium
    n 1: one of a pair of fleshy appendages of a polychete annelid
         that functions in locomotion and breathing