Meaning of ABOUT in English
(INTENDING) [adjective] [after verb; + to infinitive; not gradable] - having the intention of doing something immediately or almost starting to do somethingShe was about to leave when Mark arrived so she stayed a little longer. [after verb; + to infinitive]He looked as if he was about to burst into tears.I'm not about (= I am strongly determined not) to say I'm sorry to him after the way he's behaved.
Cambridge English vocab. Кембриджский английский словарь. 2012