The area of memory attached to a Unix prOcess by the brk and sbrksystem calls and used by mallOc 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}. [Jargon File] (1995-12-28)