Le bide is a colloquial synonym of ventre, “belly”.
J’ai failli me prendre un coup de couteau dans le bide !
I almost got stabbed in the belly!
Je me suis mis au sport pour perdre mon gros bide.
I began working out to lose my fat belly.
Un bide is also something completely unrelated: a failure, a fiasco. It is usually applied to shows or movies. Bide is the perfect word to describe the embarrassing situation when you tell a joke and nobody laughs.
Son dernier album a été un bide complet.
His last album was a total fiasco.
Listen to the examples: