(idiomatic, with infinitive verb) Indicates something that will happen very soon; indicates action that is imminent.
He's standing at the edge, and I think he's about to jump.
She seemed about to say something.
(as negative 'not about to', informal, originally US, Canada) Indicates that one has no intention of doing the stated thing at any time in the future.
I'm not about to let the lockdown stop me from going to the beach every day.
I'm not about to impose laws on people who disagree with them.
(obsolete in affirmative) Indicates that one is preparing or planning to do the stated thing at some time in the future, not necessarily imminently. [from ca. 1150—1350 to late 18th c.]
Source: en.wiktionary.orgI have looked in the mirror every morning and asked myself: "If today were the last day of my life, would I want to do what I am about to do today?" And whenever the answer has been "No" for too many days in a row, I know I need to change something. Steve Jobs
I've always tried to go a step past wherever people expected me to end up. I'm not about to change now. Beverly Sills
I am about to take my last voyage, a great leap in the dark. Thomas Hobbes
A word about to be spoken is like a stone that is ready to be thrown. Bulgarian Proverb
When a king is about to lose his power his orders burn more intensely than fire. Tibetan Proverb
When the white man is about to leave a garden for good, he wrecks it. Yoruba Proverb