The Collaborative International Dictionary of English v.0.48:

Autoclastic \Au`to*clas"tic\, a. [See Auto-; Clastic.]
   (Geol.)
   Broken in place; -- said of rocks having a broken or
   brecciated structure due to crushing, in contrast to those of
   brecciated materials brought from a distance.
   [Webster 1913 Suppl.]