Adventure is experience outside the ordinary. Not just going someplace, but doing something outside the ordinary.
I recently went on an adventure filled with many little adventures. I moved to Canada for a while. I embarked on a 4 day train journey, shot a rifle, worked in a different country, drove on the wrong side of the road legally, paid 25 dollars for the most amazing breakfast I've ever had, climbed a killer mountain, saw a moose (had to wade through a freezing lake to get a decent photo.) Adventure is going some place you haven't experienced or even doing something you haven't done before.
Adventures are not always good adventures, there can be bad ones too, that leave you running and screaming at the top of your lungs, narrowly avoiding death. However you look back and go WOW. That was an adrenaline rush!
I would consider myself adventurous, as the only thing you have in life IS experience from the moment your born screaming to the last shaky breath you take. People, things, computers, pets are all tangible. Make it count.