I use the term meditation when I’m trying to let go of thought. For me that means that I’m trying to shift more to a state where I’m aware of my thoughts but I’m not getting pulled in by them or having them dominate my awareness like huge ocean waves overwhelming a rowboat. I use the word contemplation when I’m focusing on an idea or situation to deepen my understanding or get a new perspective of it.
Different people will give you different answers to this. Here are a few definitions from around the web.
the act of giving your attention to only one thing, either as a religious activity or as a way of becoming calm and relaxed
…meditation is a state of thoughtless awareness. It is not an act of doing – it is a state of awareness. We are either in this state or we are not, regardless of what we are doing in life. Truly, a man can be in meditation while doing his day’s labors as another man can be very far from meditation while sitting in a lotus posture on the top of a mountain.
Meditdation means awareness. Whatever you do with awareness is meditation. “Watching your breath” is meditation; listening to the birds is meditation. As long as these activities are free from any other distraction to the mind, it is effective meditation.