Common definitions of Pearl include:
A small, most often round and hard object formed of calcium carbonate within the tissue of a living mollusk. Pearls can be found and/or cultivated in salt or freshwater. They are the state gemstone of Kentucky and Tennessee, and the birthstone for the month of June.
Something at its finest. Referring to the most valuable and precious example of something, as in "pearl of wisdom."
Earl "The Pearl" Monroe, N.B.A. basketball star who played for the New York Knicks from 1971-1980.
The Pearl a 1947 novella by John Steinbeck. Considered a classic folktale.
The Pearl: Album name and nickname of Janis Joplin, famous singer who died young of a drug overdose.
Related Pearl Resources
About.com Geology State Gemstone [1]
About.com Jewelry Birthstone [2]
NBA.com Earl Monroe [3]
About.com Classic Lit Steinbeck's The Pearl [4]
Official site Janis Joplin [5]
Maybe add a definition of Perl? http://perl.about.com/