Webster's Revised Unabridged Dictionary · 1913

belly up

belly up , intransitive verb

to approach (a counter) and stand in front of it; -- used mostly in the phrase belly up to the bar (that is to a counter in a saloon).

belly up , adjective

[from analogy to the position of a floating dead fish.]

defunct; bankrupt; -- used mostly of commercial organizations; often used in the phrase go belly-up, that is to go bankrupt.

Also: belly-up