The Collaborative International Dictionary of English v.0.48:

Phleum \Phle"um\, prop. n. [NL., fr. Gr. ? a kind of marsh
   plant.] (Bot.)
   A genus of grasses, including the timothy (Phleum
   pratense), which is highly valued for hay; cat's-tail grass.
   --Gray.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Phleum
    n 1: grasses native to temperate regions [syn: Phleum, genus
         Phleum]