The Collaborative International Dictionary of English v.0.48:

Impignorate \Im*pig"no*rate\ ([i^]m*p[i^]g"n[-o]*r[=a]t), v. t.
   [LL. impignoratus, p. pl of impignorare to pawn. See
   Pignoration.]
   To pledge or pawn. [Obs.] --Laing.
   [1913 Webster]