WordNet (r) 3.0 (2006):

Crataegus laevigata
    n 1: thorny Eurasian shrub of small tree having dense clusters
         of white to scarlet flowers followed by deep red berries;
         established as an escape in eastern North America [syn:
         whitethorn, English hawthorn, may, Crataegus
         laevigata, Crataegus oxycantha]