to look at or watch sth while doing sth else, especially in a secret way so that other people do not notice :
During his talk, most of the delegates had one eye on the clock.
to look at or watch sth while doing sth else, especially in a secret way so that other people do not notice :
During his talk, most of the delegates had one eye on the clock.
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005