The Collaborative International Dictionary of English v.0.48:

Extrusion \Ex*tru"sion\, n.
   The act of thrusting or pushing out; a driving out;
   expulsion.
   [1913 Webster]

WordNet (r) 3.0 (2006):

extrusion
    n 1: something that bulges out or is protuberant or projects
         from its surroundings; "the gun in his pocket made an
         obvious bulge"; "the hump of a camel"; "he stood on the
         rocky prominence"; "the occipital protuberance was well
         developed"; "the bony excrescence between its horns" [syn:
         bulge, bump, hump, swelling, gibbosity,
         gibbousness, jut, prominence, protuberance,
         protrusion, extrusion, excrescence]
    2: squeezing out by applying pressure; "an unexpected extrusion
       of toothpaste from the bottom of the tube"; "the expulsion of
       pus from the pimple" [syn: extrusion, expulsion]