to not be able to identify what is wrong or different about a particular situation :
There was something odd about him but I couldn't put my finger on it.
to not be able to identify what is wrong or different about a particular situation :
There was something odd about him but I couldn't put my finger on it.
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005