underbelly

1 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 Synonyms of underbelly demimonde, demiworld, half-world, netherworld, underworldWords Related to underbelly abyss, depths

2 the side or part facing downward from something the underbelly of the old submarine is in bad shape Synonyms of underbelly bottom, underbody, underpart, underside, undersurfaceWords Related to underbelly belly, sole, toe; base, floor, foot, ground, seat, underpinning; undercarriageNear Antonyms of underbelly acme, apex, climax, crest, crown, culmination, height, high-water mark, meridian, peak, pinnacle, roof, summit; cusp, head, point, tip, tip-top, zenithAntonyms of underbelly face, top

3 a vulnerable point the vast, thinly guarded southern border was obviously the underbelly of the nation's line of defense Synonyms of underbelly back, chink, jugular, soft spot, Achilles' heelWords Related to underbelly downfall, ruin, undoing; hamartia, tragic flaw