gem in WordNet English dictionary

1. a precious or semiprecious stone incorporated into a piece of jewelry
   jewel  gem  precious stone 
   
2. art highly prized for its beauty or perfection
   gem  treasure 
   
3. a sweet quick bread baked in a cup-shaped pan
   muffin  gem 
   
4. a person who is as brilliant and precious as a piece of jewelry
   jewel  gem 
   
5. a crystalline rock that can be cut and polished for jewelry
   "he had the gem set in a ring for his wife"; "she had jewels made of all the rarest stones"
   gem  gemstone  stone