The Collaborative International Dictionary of English v.0.48:

Poa \Po"a\, n. [NL., fr. Gr. ? grass.] (Bot.)
   A genus of grasses, including a great number of species, as
   the kinds called meadow grass, Kentucky blue grass, June
   grass, and spear grass (which see).
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

meadowgrass \meadowgrass\, meadow grass \meadow grass\n.
   Any of various grasses that thrive in the presence of
   abundant moisture, especially those of the genus Poa,
   common in meadows, and of great value for hay and for
   pasture. See Grass.
   [1913 Webster + WordNet 1.5] meadowlark

WordNet (r) 3.0 (2006):

meadow grass
    n 1: any of various grasses that thrive in the presence of
         abundant moisture [syn: meadowgrass, meadow grass]