Having a "strong stomach" means being able to handle or tolerate things that are difficult, disgusting or disturbing without feeling queasy or sick. Full definition
I like to think that I have a pretty strong stomach for risk. (alephblog.com)
But the truth is that in most (but not all) cases people actually suffer from weak stomach acid and they need stronger stomach acid to properly digest foods. (blog.bartonpublishing.com)
This is because younger women typically have tighter, stronger stomach muscles for their baby bump to hide behind. (momtricks.com)