arena
     n 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" [syn: {sphere}, {domain}, {area}, {orbit},
           {field}]
     2: the central area of an ancient Roman amphitheater where
        contests and spectacles were held; especially a
        sand-strewn area
     3: a large structure for open-air sports or entertainments
        [syn: {stadium}, {bowl}, {sports stadium}]
     4: a playing field where sports events take place [syn: {scene
        of action}]
Source: WordNet® 2.0

arena n. [common; Unix] The area of memory attached to a process by
   `brk(2)' and `sbrk(2)' and used by `malloc(3)' as dynamic storage. So
   named from a `malloc: corrupt arena' message emitted when some early
   versions detected an impossible value in the free block list. See
   {overrun screw}, {aliasing bug}, {memory leak}, {memory smash}, {smash
   the stack}.


Source: The Jargon File