Something overwhelming is very intense and hard to deal with: overwhelming events make people worried and stressed out.
It's hard to overcome overwhelming things. If you feel an overwhelming need to laugh, you're probably going to laugh. If you have an overwhelming feeling of sadness, you'll probably cry. An overwhelming amount of homework is almost impossible to get done. Adults who work, have families, and struggle to pay the bills feel like their lives are overwhelming. A tornado or hurricane is an overwhelming force of nature. When something is overwhelming, there's not much you can do against it.