underbelly

American  

[uhn-der-bel-ee] / ˈʌn dərˌbɛl i /

noun

plural

underbellies

1. the lower abdomen; posterior ventral area, as of an animal's body.

2. the lower surface of an object; underside.

   the underbelly of an airplane.

3. a vulnerable area; weak point.

   an attack on the soft underbelly of Europe.

4. a dark, seamy, often hidden area or side.

   a police officer continually exposed to the underbelly of society.

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underbelly British  

/ ˈʌndəˌbɛlɪ /

noun

1. the part of an animal's belly nearest to the ground

2. a vulnerable or unprotected part, aspect, or region

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Etymology

Origin of underbelly

First recorded in 1600–10; under- + belly

Explanation

The underbelly of something is its secret weakness, something about it that's not protected from harm. Once a computer hacker discovers a network's underbelly, they're easily able to hack into it. Literally, an underbelly is just that: it's the abdomen of an animal, the soft lower belly. Often, that's also the most vulnerable part of an animal's body, since it contains major organs, and it's where the figurative meaning comes from. An alternate informal definition is "a hidden, criminal part of society," like the underbelly of a city where criminals trade stolen goods.

Example Sentences

Maybe it was the underbelly of all of the bravado and power-seeking—some desire to counter all the validation with the humiliation of knowing that, deep down, he’s just a revolting little worm.

From Slate • Apr. 15, 2026

Where the first wave of bands that emerged from downtown were more traditionally rock and roll and melodic, No Wave was the louder, darker, discordant underbelly and the logical next step.

From Salon • Apr. 14, 2026

And she suggests that the current state of the Epstein files exposes a darker underbelly.

From BBC • Feb. 6, 2026

But those earnings have an ugly underbelly: ever-bigger losses at the generative AI startups that spend big on chips and data centers supplied by the profitable public companies.

From The Wall Street Journal • Nov. 13, 2025

We bounce over a boulder so big, I hear it scrape on our underbelly.

From "Dry" by Neal Shusterman and Jarrod Shusterman

Related Words

• basement
• bed
• floor
• ground
• seat
• underside