It means something along the lines of a bulging, swelled-out abdomen. The word generally refers to the belly of a pregnant woman.
So big!!
When are you giving birth!?
Ulp—!?
Urk—!?
This is a gravid belly.
/botebara/
Eh!?
You have a big belly, but not because you're pregnant!?
Waaaaaaaaah! NOSHIROOOOO!
I'll start dieting next weeeeeek!!
Starting today,
you mean.At least make it tomorrow...And I've warned you so many times too, Agano-nee.
Now you ended up with a bloated stomach that can be mistaken for a pregnant woman's, thanks to your frequent unhealthy lifestyle choices.