The Collaborative International Dictionary of English v.0.48:

Concision \Con*ci"sion\, n. [L. concisio: cf. F. concision. See
   Concise.]
   A cutting off; a division; a schism; a faction. --South.
   [1913 Webster]

WordNet (r) 3.0 (2006):

concision
    n 1: terseness and economy in writing and speaking achieved by
         expressing a great deal in just a few words [syn:
         conciseness, concision, pithiness, succinctness]