1 [countable] British English
a serious road or railway accident - used especially in newspapers [= crash]:
Young boy hurt in car smash.
2 [countable] also smash hit
a new film, song etc which is very successful:
a box-office smash (=a film which many people go to see at the cinema)
a hard downward shot in tennis or similar games
the loud sound of something breaking
He heard the smash of glass.