Does anyone know a good online "reverse" musical dictionary where it gives you a musical term that translates to the English query you want? (say your query is "softly" to give "piano") Rather, does such a source exist?

I just own four language dictionaries: English-German, English-French, English-Italian, and English-Spanish

Music terms aren't special, they're just normal words in other languages.

That's a neat solution but, yikes, it does mean having four heavy books! I think score-writing is a piece of art in its own right, having terms written in English is fine but there are certain terms that will lose their "artistic" touch in English when the "musical" equivalents (whatever language) are prevalently used. (and I'm one of those pedants who use italics for words from a non-English language on the score, and italics goes down very well with being artistic. Anyhow, enough of my excesses! )

I wish someone would compile a reverse dictionary of commonly used musical terms, though. There will be time when I forget the word calando and spends an hour tearing my hair trying to remember the word that begins with a C and sounds a bit like colander...

This is not exhaustive but it's a start - a music thesaurus:

http://www.spindrift.com/Thesaurus/index.html