WordNet (r) 3.0 (2006):

class Tardigrada
    n 1: in some classifications considered a separate phylum:
         microscopic arachnid-like invertebrates living in water or
         damp moss having 4 pairs of legs and instead of a mouth a
         pair of stylets or needlelike piercing organs connected
         with the pharynx [syn: Tardigrada, class Tardigrada]