The Collaborative International Dictionary
Desponsate
Desponsate \De*spon"sate\, v. t. [L. desponsatus, p. p. of
desponsare, intens. of despondere to betroth. See Despond.]
To betroth. [Obs.]
--Johnson.
Wiktionary
desponsate
vb. (context transitive archaic English) To betroth.