a social sphere that exists outside of the mainstream <unable to get work in mainstream films, the actor ended up in Hollywood's underbelly—the porn industry>
the side or part facing downward from something <the underbelly of the old submarine is in bad shape> Near Antonyms acme
, high-water mark
a vulnerable point <the vast, thinly guarded southern border was obviously the underbelly of the nation's line of defense>
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