WordNet sense 1 (European hawthorn having deeply cleft leaves and bright red fruits; widely cultivated in many varieties and often grown as impenetrable hedges; established as an escape in eastern North America):

Crataegus monogyna

WordNet sense 2 (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):

may, whitethorn, Crataegus laevigata, Crataegus oxycantha