sponsion
Webster's Dictionary (GCIDE)
Sponsion \Spon"sion\ (-sh[u^]n), n. [L. sponsio, fr. spondere, sponsum, to promise solemnly.]
1.The act of becoming surety for another. [1913 Webster]
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. [1913 Webster]