What does the term "baby pangs" mean?

You’ve got it. Another term is “I can hear my biological clock ticking’. Here is an example of both of them.

I have two daughters, and I constantly have “baby pangs”. I would really LOVE to have another baby, I would LOVE to go through pregnancy and childbirth again. I want it so bad I can imagine vividly the feel of nursing another newborn, and I can feel that invisible, desired baby kick me sometimes. It’s emotionally awful, really.

I have had them to one extent or another since I was about 15 years old.
They have nearly gone away now. I have four children and two grand children.
They were very strong at times, a bit like @WillWorkForChocolate describes.
Now I am thankful that I no longer have to be responsible for the total care of an infant.
I don’t have the energy for that any more. I can love them and send them back to their parents.

I have felt baby pangs before, but it’s only when I see an attractive man my body wants to mate with, even more so if they are good with kids. It’s pretty much like this.

Yearning for a child. I got those late in life.

Yup. A good remedy for this is babysit a 2 year old.

I believe it’s a real physical as well as emotional occurrence in many women. (I don’t know if it is in men.)
It can be very strong and really as @filmfann said, if you can still want another baby when you already have a two year old…
that is powerful stuff.