Definitions of arena:

• noun:   a playing field where sports events take place
• noun:   the central area of an ancient Roman amphitheater where contests and spectacles were held; especially a sand-strewn area
• noun:   a large structure for open-air sports or entertainments
• noun:   a particular environment or walk of life
• name:  A surname (rare: 1 in 50000 families; popularity rank in the U.S.: #6666)