OED

If you don't have a dictionary for the definitions, may I suggest Oxford English Dictionary Online. We all have access to it from the library website, and it is a great resource. I cannot emphasize this enough. It gives you not only the definition of the word, but also the entymology, and how the meaning has developed through time. It then gives quotations from various works of literature and history to illustrate the change in meaning. This is a really cool dictionary. Here is a link to get access to it :
http://libraries.colorado.edu/search/toxford+english+dictionary/toxford+english+dictionary/1%2C2%2C2%2CB/frameset&FF=toxford+english+dictionary+online&1%2C1%2C