1. create or bring up a problem that will cause or lead to many other troubles
don't open that can of worms
A 'can of worms' is an idiomatic expression used to talk about a situation that once approached is likely to lead to more problems and complications. If something is a 'can of worms' it is more complicated or troublesome than it might seem at first. "Raising salaries might seem like a sensible solution but is a can of worms with knock-on effects including inflation, making business difficult for small and medium companies and demands for higher pay in other sectors." This is an idiomatic expression you will hear used in social and professional contexts.