The phrase "rambling about" is correct and is used in written English.
It is used to describe speaking in an unfocused or disorganized way, with many digressions and repetitions. For example, "He was rambling about insignificant details that held no relevance to the conversation."
His incoherent rambling about team experiences from his grad student days reversed his entirely positive interview.
"After all" — dictatorial types, in moments of crisis, have a bad tendency to start rambling about love.
Ms. Hinnant then began rambling about horse breeding and other topics, people in court said.
And then the guy starts rambling about how George W. Bush had blown up the World Trade Center.
(This was a day or two before Sununu began rambling about how Barack Obama had to learn to be American).
Trump wasn't alone on this one; it's not a case of him just causing trouble with his phone and Twitter account, rambling about bad hombres.
He used the word exciting 17 times in a 21-minute news conference, smiling and laughing and rambling about the virtues of his new team.
Recently, a man on the last car of a downtown A train was rambling about the Sept. 11 attacks, justifying them and saying that more were coming.
He does not write like a swivel-eyed loon rambling about Obamunism (although, inevitably, there's an unsavoury fascination with Jewish influence).
The sun makes an early, brief appearance in "The Exiles," when the camera surveys the downtown multitudes before narrowing in on Yvonne, rambling about the child in her belly and the husband at home.
I usually end up rambling about an interesting drama that might be worth seeing if you like that sort of thing; before long, the person listening to me isn't listening any more.
