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|n. pl.||1.||(Zool.) A very extensive order of Annelida (segmented worms), characterized by the presence of lateral setæ, or spines, on most or all of the segments. They are divided into two principal groups: Oligochæta, including the earthworms and allied forms, and Polychæta, including most of the marine species.|
Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.