The phrase "about to fall out" is correct and usable in written English.
It can be used to describe something that is on the verge of detaching or coming loose, often in a physical context.
Example: "The old tree branch was so weak that it was about to fall out, posing a danger to anyone walking underneath it."
Alternatives: "on the verge of coming loose" or "ready to drop off".
"It's gotten so bad that it's actually destroying the sport and eating out the root of the sport from the bottom, and the bottom is about to fall out".
The British Prime Minister David Cameron and Facebook founder and CEO Mark Zuckerberg look like they could be about to fall out already.
Apatow added that the "best-case scenario" is that the president was speaking oddly because his dentures are about to fall out and he doesn't want to admit he has them.
But Grandma not knowing Martha's name, Grandma lying in bed sucking on her unmoored jaw, Grandma with all of her teeth about to fall out—I almost lost it.
Ms. Weymouth took the helm just as the bottom was about to fall out of the economy.
What predicates should be included in our ontology for any of these claims about "most properties" to fall out?
"So if it's not safe for me jumping down, then my uterus is going to fall out, what about the organ on the outside of the body?" For years, nobody listened.
In doing so he saved their lives, but as his provisions were rapidly exhausted he was forced to return to port to resupply at the point at which Cape François was about to fall, and so missed out on a considerable sum of prize money.
Another "spark" for Kurds' fury was Erdoğan's phrase, which to Kurdish ears sounded like schadenfreude: "Look, Kobani is now about to fall!" Also, Dicle pointed out, the refusal of Erdoğan's close circle to link Kobani with the peace process in Turkey led to the tipping point.
Somewhere between Woody Allen's Soon-Yi surprise and Dr. Melfi's failure to slay Tony Soprano's sociopathic demons, therapists of the old-fashioned, "lie back on the couch and tell me about your childhood" school began to fall out of fashion.
