The Collaborative International Dictionary of English v.0.48:

Cerastium \Cerastium\ n.
   a genus of weedy plants of the pink family, comprising the
   mouse-ear chickweeds.

   Syn: genus Cerastium.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Cerastium
    n 1: mouse-eared chickweed [syn: Cerastium, genus Cerastium]