can of worms

American  

noun

1. Informal. a source of many unpredictable or unexpected problems.

   Buying a company we know nothing about would be opening up a whole new can of worms.

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can of worms Idioms  

1. A complex unexpected problem or unsolvable dilemma, as in Tackling the budget cuts is sure to open a can of worms. This expression alludes to a container of bait used for fishing, which when opened reveals an inextricable tangle of worms. [1920s]

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Etymology

Origin of can of worms

First recorded in 1965–70

Example Sentences

What remains to be seen now is whether a wider can of worms has been opened.

From BBC • Oct. 30, 2025

One of the theater’s more prominent sociopaths gets a makeover in “Hedda,” director Nia DaCosta’s reimagining of “Hedda Gabler,” with an approach that opens up the play—and an interpretive can of worms.

From The Wall Street Journal • Oct. 28, 2025

Nudleman prefers to use his Amazon Fire Stick’s voice search feature to look for specific titles he’s interested in, but that experience is its own can of worms.

From Salon • May 22, 2025

That’s a can of worms for future parasite research.

From Science Magazine • May 7, 2024

This one hangs out in the same crowd with hook, line, and sinker and lock, stock, and barrel. can of worms.

From "Woe Is I" by Patricia T. O'Conner