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

See Examples For:

can of worms

Well, you’re opening up a whole can of worms.

From Los Angeles Times ● Jul. 2, 2026

Or a can of worms best left unopened?

From BBC ● Jun. 23, 2026

Because no matter how successful these ventures look from the outside, the truth is you take the lid off the can and inside it’s a can of worms.

From The Wall Street Journal ● May 23, 2026

X gives blue-check verification to anyone willing to pay for its premium services; this has opened a can of worms, especially among pop culture and nostalgia accounts.

From Slate ● Sep. 1, 2024

I had twenty- three cents—a dime I had earned running errands for my grandpa, and thirteen cents a fisherman had given me for a can of worms.

From "Where the Red Fern Grows" by Wilson Rawls