Unbutton \Un*but"ton\, v. t. [1st pref. un- + button.]
To loose the buttons of; to unfasten.
[1913 Webster]
31 Moby Thesaurus words for "unbutton": cast off, detach, disengage, doff, free, liberate, loose, loosen, release, remove, take off, unbar, unbind, unbolt, unbuckle, unchain, unclasp, undo, unfasten, unfetter, unglue, unlace, unlatch, unleash, unlock, unloose, unloosen, unstick, unstrap, untie, weigh anchor