What Is a Seasoned Veteran?

The man who survived pepper spray and mustard gas is now a seasoned veteran. All i did was take a day off and stay in bed. Why did the frogs have to die? For they were sacrificed for the good, to the gods of learning english. So if youare a veteran, it means you're someone who has experience of doing things. But also, seasoned could mean something else. It's just like another way of emphasizing the meaning of it.