Happy Biiirthday Daaay
Dear Lee-O-Nardoo...
Light the candles for one
of the original Idea Guys
Answers.com certainly has DaVinci defined -- check it out.

Something else you may want to check out is How To Think Like Leonardo DaVinci. Excellent book that does it's best to outline DaVinci's seven guiding principles of discovery:
Curiosita: Seek the truth
Dimostrazione: Take responsibility
Sensazione: Cultivate awareness
Sfumato: Engage the shadow
Arte/Scienza: Balance the masculine and feminine principles
Corporalita: Integrate body and spirit
Connessione: Practice love

Inspiring stuff!