The Collaborative International Dictionary of English v.0.48:

Unconformity \Un`con*form"i*ty\, n.
   1. Want of conformity; incongruity; inconsistency. --South.
      [1913 Webster]

   2. (Geol.) Want of parallelism between strata in contact.
      [1913 Webster]

   Note: With some authors unconformity is equivalent to
         unconformability; but it is often used more broadly,
         for example, to include the case when the parallelism
         of strata once conformable has been disturbed by
         faulting and the like.
         [1913 Webster]