what does "anthill-size bump"mean?
Sadie stirred herself to stand from her sprawl on the kitchen floor so she and Barbie could sniff at each other.
“Where’s the baby?”
“Right here.” Tricia patted her anthill-size bump. “Big sister’s up-stairs having a Sunday snuggle with Daddy. I’m getting a window of quiet and the single stingy cup of coffee I’m allowed a day. You can have one, too, then help me hide eggs.”
“I can do that, after I take the dogs for a walk.”what does this "bump"mean?