parapodium(n = noun.animal) - one of a pair of fleshy appendages of a polychete annelid that functions in locomotion and breathing;
is a kind of appendage, extremity, member

   One of the lateral appendages of an annelid; -- called also foot tubercle. [1913 Webster]
" They may serve for locomotion, respiration, and sensation, and often contain spines or setæ. When well developed, a dorsal part, or notopodium, and a ventral part, or neuropodium, are distinguished." [1913 Webster]