arena in WordNet English dictionary

1. a particular environment or walk of life
   "his social sphere is limited"; "it was a closed area of employment"; "he's out of my orbit"
   sphere  domain  area  orbit  field  arena 
   
2. a playing field where sports events take place
   arena  scene of action 
   
3. a large structure for open-air sports or entertainments
   stadium  bowl  arena  sports stadium 
   
4. the central area of an ancient Roman amphitheater where contests and spectacles were held; especially an area that was strewn with sand
   arena