Wiktionary
accident waiting to happen
n. (context idiomatic English) A thing or situation which is almost certain to eventually lead to an accident
Usage examples of "accident waiting to happen".
He was an accident waiting to happen, and he hadn't had to wait long.
Guys like Henry and his buddies were an accident waiting to happen.
Even after all Ian's hard work, when put next to the fleet of white Savoy Enterprises vehicles that the ranch hands used, his ancient truck looked like an accident waiting to happen.
I would be asking for it, I would get what was coming to me, I would be an accident waiting to happen.
What was taking place out on the terrace was an accident waiting to happen.
An unmanned bulb is an accident waiting to happen, as Mr Holland used to say.