Here's how I like to look at it... Our knowledge and perceptions all fall back on our senses. In my eyes, our senses are extremely unrealiable and can be rather deceptive at times, but... that's not the primary reason why I think the way I do. The reason why I believe that there is no such thing as objectivity is that everything we deem as knowledge and truth are merely made up of terms and observations that have come from humanity. Humanity does not have the authority to establish universal truths... mainly due to the unreliability of our senses.
We have a much different way of perceiving time in comparison to that of other organisms. We also have a different way of perceiving the universe all together, thus making (what we perceive as) reality subjective in comparison to that of the universe. So... we can't truly know anything. We just go by what our senses tell us.
What I just described to you could be considered epistemological nihilism... a form of nihilism that I'm a bit weary about. Feel free to challenge that theory because I'm not quite sure about it myself.
On another note... existential nihilism is, yes, what you described: there is no objective meaning of life. I've heard the term "anti-nihilist" used several times in a book I'm reading, but I'm not entire sure what that is. As for myself... I am an existential, moral, and political nihilist... all falling under passive nihilism (which means I accept society for what it is and have no desire to attempt to change it).
Just a quick comment about epistemological nihilism: a person who is one can't make assertions of any sort. So if you were one, you couldn't assert that you are one, and couldn't know that you are one. You couldn't know anything. Even your perceptions would have to be regarded as meaningless. Simply because there would be no meaning at all. Kind of like non-existence, except that the idea of non-existence is meaningful and ideas aren't allowed (since they have meaning).
It's the ultimate non-position.