Source : Webster's Revised Unabridged Dictionary (1913)

Pretermission \Pre`ter*mis"sion\, n. [L. praetermissio. See
   {Pretermit}.]
   1. The act of passing by or omitting; omission. --Milton.

   2. (Rhet.) See {Preterition}.

Source : WordNet®

pretermission
     n : letting pass without notice