Source : Webster's Revised Unabridged Dictionary (1913)

Fair catch \Fair catch\ (Football)
   A catch made by a player on side who makes a prescribed
   signal that he will not attempt to advance the ball when
   caught. He must not then be interfered with.

Source : WordNet®

fair catch
     n : (American football) a catch of a punt on the fly by a
         defensive player who has signalled that he will not run
         and so should not be tackled