Source : Webster's Revised Unabridged Dictionary (1913)

Sponsion \Spon"sion\, n. [L. sonsio, fr. spondere, sponsum, to
   promise solemnly.]
   1. The act of becoming surety for another.

   2. (Internat. Law) An act or engagement on behalf of a state,
      by an agent not specially authorized for the purpose, or
      by one who exceeds the limits of authority.