They have that phrase... 'above and beyond the call of duty'. If that applies to an action, there's a pretty good chance of it being classed as heroic.

Essentially, heroism is putting oneself in harm's way, in order to accomplish some higher objective. The harm can be physical, or mental...

Now, the 'higher objective' changes in this subjective world we live in - these days, saving the life of another is pretty much the only deed that satisfies, whereas there was once a time when one's honour was sufficient to drive one to such an act. And for some people, another's life is not important, it seems.