Everyone needs a dictionary of musical terms at different points in their playing.  From tempo marking indications to types of musical dance forms, you will need to look up various musical terms quite often.  If you don't actually own your own dictionary of terms, there are numerous music dictionary resources handy on the Internet to use. Here are a few to help you take a look!

• Virginia Tech Multimedia Music Dictionary -- Terms are listed in the left margin.  Very comprehensive with pronunciation of terms.  Also includes quizzes, examples, and simulations.
• Music Dictionary -- From ThinkQuest, very basic set of terms dictionary.  Includes Tempo Terms and Dynamic Symbols separately.
• Dolmetsch Music Dictionary Online -- Listings by letter, quite comprehensive.  Includes many terms drawn from the many world music traditions, jazz, rock, pop and related musical genres.  Symbol and composer links separate.
• Essentials of Music Glossary -- A glossary of essential musical terminology in a smart-looking layout by alphabet.  Includes sound files.
• Music Dictionary -- Has basic terminology by letter name, good long list.  A bit cluttered with ads.
• Classics for Kids Musical Dictionary -- A dictionary of musical terminology designed for children with audio/visual examples of each term.
• Musical Terminology -- If it's COLOR that you want with your terminology , then use this dictionary.  Very colorfully laid out, with each letter of the alphabet section in a different color.  Aesthetically eye-catching.