The Collaborative International Dictionary of English v.0.48:
Unbe \Un*be"\ ([u^]n*b[=e]"), v. t. [1st pref. un- + be.] To cause not to be; to cause to be another. [Obs. & R.] [1913 Webster] How oft, with danger of the field beset, Or with home mutinies, would he unbe Himself! --Old Play. [1913 Webster]