The Collaborative International Dictionary of English v.0.48:

Outcrop \Out*crop"\, v. i. (Geol.)
   To come out to the surface of the ground; -- said of strata.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Outcrop \Out"crop`\, n. (Geol.)
   (a) The coming out of a stratum to the surface of the ground.
       --Lyell.
   (b) That part of inclined strata which appears at the
       surface; basset.
       [1913 Webster]

WordNet (r) 3.0 (2006):

outcrop
    n 1: the part of a rock formation that appears above the surface
         of the surrounding land [syn: outcrop, outcropping,
         rock outcrop]
    v 1: appear on the surface, come to the surface on the ground;
         "Big boulders outcropped"