Really. It's not so hard.  

Approach it like trying to define skiing. 

No one has trouble with that, do they? 

I put on some boots, buckle them up, then insert the boots (with my feet in them) into bindings that attach me to some skis. (Yes, I can define what a ski is too.) Then I get on some kind of conveyance (examples include chair lifts and gondolas) that takes me to the top of a hill. I then slide down the hill on my skis, trying to maintain control until I get to the bottom of the slope. I might fall, hopefully not getting injured. If I'm okay, I get up and continue my trip down the mountain. If I get injured the ski patrol comes and gets me and takes me to the hospital. That's skiing.  

Now journalism.  

I get an idea for a story or someone gives me one. Do a little searching on the web, call a few people. Take notes on what I hear. Call some other people or send them emails. Write up the notes on my computer. Organize them into a sequence. Then, I optionally offer it for review to other people to get their opinions and they possibly rewrite it, or I incorporate their feedback and make changes. This is called editing. This process iterates a few times. Then the story is published, usually on a website, and possibly at some later time on paper.  

If you do this then you're doing journalism. If you do something else, it's something else. It's not good or bad. But this is what we call journalism.