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

Support collapsed after a partial core meltdown in 1979 at the Three Mile Island plant in Pennsylvania led to several days of panic, heightening awareness of potential safety risks.

From The Wall Street Journal • Jun. 9, 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

Written just a few days after the 1979 accident at the Three Mile Island nuclear power plant, the worst such accident in U.S. history to date.

From Salon • Feb. 10, 2026

Old nuclear plants such as Three Mile Island are being recommissioned.

From Barron's • Dec. 24, 2025

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