Obviously, I am not the only who had tried to look up "instagram" on Google Dictionary:

I was read this sentence "I instagrammed a photo of the ..." which was the reason I thought "instagram" could be a word. Well, it is not. By the way, Google Dictionary should not suggest in the same way as normal Google Search does. It shall only gives you suggestions that it has definitions.

I didn't find it on instagr.am either, but its About Us page hints a bit [emphasis added]:

Instagram came from that inspirationcould we make sharing your life as instant and magic as those first Polaroid pictures must have felt?

Not sure where the "gram" was from, "photogram," doesn't look so?

You probably have heard that Facebook bought Instagram for one billion dollars, it's been all over on Internet, discussed if that price was worth. To be honest, I don't really care about that deal, I don't own an iPhone nor do I use Facebook. Just someone wants to learn a new word whenever he has a chance and is up to that.

So, what's the definition of it? Doesn't matter since it is not a real word, only thing I need to know it's what Instagram is for and I know that already.

Whenever I need to turn a non-word into a not-really-a-word verb, I would suffix "'d," for example "instgram'd." I think it is a better way to write when you try to give readers a feeling of something.