The Collaborative International Dictionary of English v.0.48:

Crataegus \Cra*t[ae]"gus\ (kr?-t?"g?s), n. [NL., fr. Gr.
   krataigo`s.] (Bot.)
   A genus of small, hardy trees, including the hawthorn, much
   used for ornamental purposes.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Crataegus
    n 1: thorny shrubs and small trees: hawthorn; thorn; thorn apple
         [syn: Crataegus, genus Crataegus]