gribble
Webster's Dictionary (GCIDE)
Gribble \Grib"ble\, n. [Cf. Prov. E. grib to bite.] (Zool.) A small marine isopod crustacean (Limnoria lignorum or Limnoria terebrans), which burrows into and rapidly destroys submerged timber, such as the piles of wharves, both in Europe and America. [1913 Webster]
The Jargon File
gribble n.
Random binary data rendered as unreadable text. Noise characters in a data stream are displayed as gribble. Dumping a binary file to the screen is an excellent source of gribble, and (if the bell/speaker is active) headaches.