I need a new dictionary

I am currently reviewing several papers that were submitted to a conference that will be held this summer. This is part of life as a grad student in my research group. Our advisor receives papers that must be reviewed for a conference, the final decision based on the review is whether or not to let the paper into the conference. We students read the papers, write reviews, and then we meet with our advisor to discuss the reviews and make our decision to accept or reject the paper. This decision is passed on with combined versions of the reviews for the paper as my advisor's official opinion to the conference program committee. Reviewing the papers allows me to keep up with what others are doing in my field, and lets me practice critical reading and reviewing skills that are necessary if I accept a position in academia after I graduate. While it may have shot my plans for the week I appreciate that it is a good thing for me to do.

Now that you know what I am doing I'll get back to the topic of the post. Reading a paper last night the author's of a paper claimed at several points that their approach obviated a previous approach. I used the small student dictionary I have (about 300 5" x 7" pages) to look up obviate. The dictionary offered the one word definition "prevent". This made me deduct points because the statement was false and I assumed that the authors had tried to use a fancy word that they didn't really know. Today I get to school and check on dictionary.com and find that obviate really means "render unnecessary". That definition makes the claim accurate and my opinion of the paper much higher.

The whole point to this rambling post is that the small dictionaries people keep just aren't adequate. I need a serious dictionary for the times when I am offline and too lazy to wander to the computer and check what the all knowing Internet people say about a word.