Three Mile Island

American  

noun

1. an island in the Susquehanna River, near Middletown, Pennsylvania, SE of Harrisburg: scene of a near-disastrous accident at a nuclear plant in 1979 that raised the issue of nuclear-energy safety.

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Three Mile Island ¹ Cultural  

1. The location of an accident in 1979 in a nuclear power plant — an electrical generator powered by a nuclear reactor — in Pennsylvania. The plant underwent a partial meltdown that resulted in very little leakage of radiation into the atmosphere, panic among nearby residents, losses of billions of dollars, and intense criticism of nuclear power programs in general. (Compare Chernobyl.)

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Three Mile Island ² Cultural  

1. The location of an accident in 1979 in a nuclear power plant in Pennsylvania. The plant underwent a partial meltdown that resulted in some radiation leakage into the atmosphere, panic among nearby residents, losses of billions of dollars, and intense criticism of nuclear power programs in general.

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Compare meaning

How does three-mile-island compare to similar and commonly confused words? Explore the most common comparisons:

• Chernobyl vs. Three Mile Island

Example Sentences

The new reactors also use different technology from conventional plants, ruling out the kind of cascading disasters seen at Three Mile Island and Chernobyl, and allowing for far simpler, cheaper construction.

From Barron's • Jun. 28, 2026

Crane is part of Three Mile Island, a shuttered nuclear plant in Pennsylvania.

From Barron's • May 11, 2026

Cliff Kuang and Robert Fabricant open their book User Friendly with the cautionary tale of the Three Mile Island nuclear disaster.

From Slate • Apr. 4, 2026

Many nuclear-power plants have fewer reactors than initially planned because of spiraling costs and waning enthusiasm for the technology after the partial meltdown at Three Mile Island in Pennsylvania in the late 1970s.

From The Wall Street Journal • Feb. 12, 2026

A nuclear accident that occurred at Three Mile Island in Pennsylvania in 1979 was classified after the fact as a level 5.

From "Meltdown" by Deirdre Langeland