fence
     n 1: a barrier that serves to enclose an area [syn: {fencing}]
     2: a dealer in stolen property
     v 1: enclose with a fence; "we fenced in our yard" [syn: {fence
          in}]
     2: receive stolen goods
     3: fight with fencing swords
     4: surround with a wall in order to fortify [syn: {wall}, {palisade},
         {fence in}, {surround}]
     5: have an argument about something [syn: {argue}, {contend}, {debate}]
Source: WordNet® 2.0

fence n. 1. A sequence of one or more distinguished ({out-of-band})
   characters (or other data items), used to delimit a piece of data
   intended to be treated as a unit (the computer-science literature calls
   this a `sentinel'). The NUL (ASCII 0000000) character that terminates
   strings in C is a fence. Hex FF is also (though slightly less
   frequently) used this way. See {zigamorph}. 2. An extra data value
   inserted in an array or other data structure in order to allow some
   normal test on the array's contents also to function as a termination
   test. For example, a highly optimized routine for finding a value in an
   array might artificially place a copy of the value to be searched for
   after the last slot of the array, thus allowing the main search loop to
   search for the value without having to check at each pass whether the
   end of the array had been reached. 3. [among users of optimizing
   compilers] Any technique, usually exploiting knowledge about the
   compiler, that blocks certain optimizations. Used when explicit
   mechanisms are not available or are overkill. Typically a hack: "I call
   a dummy procedure there to force a flush of the optimizer's
   register-coloring info" can be expressed by the shorter "That's a fence
   procedure".


Source: The Jargon File