Defeat means getting beaten, or failing at doing something. Stunning in this case means that what happened was so bad that you couldn't figure out what to do next, that everything just came to a stop.
I suffered defeat at the hands of my opponent.
Waterloo
Germany
'Stunning ' is mind blowing.
Charleston, South Carolina
Charleston
He suffered a major military defeat at Waterloo.
It can mean beautiful
the first battle of bull run
The army suffered a stinging defeat in their war with Britian.
The North Suffered Serious Defeat At Both Sides.
The north suffered serous defeat at both battles