to be looking carefully for sb/sth that you expect to see, especially in order to avoid possible danger :
Be on the watch for thieves.
to be looking carefully for sb/sth that you expect to see, especially in order to avoid possible danger :
Be on the watch for thieves.
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005