The Collaborative International Dictionary of English v.0.48:

Agrostis \A*gros"tis\, n. [L., fr. Gr. ?.]
   A genus of grasses, including species called in common
   language bent grass. Some of them, as redtop (Agrostis
   vulgaris), are valuable pasture grasses.
   [1913 Webster] Agrostographic

WordNet (r) 3.0 (2006):

Agrostis
    n 1: annual or perennial grasses cosmopolitan in northern
         hemisphere: bent grass (so named from `bent' meaning an
         area of unfenced grassland) [syn: Agrostis, genus
         Agrostis]