“+ verb
Etymology: Middle English unbotonen, from un- (II) + botonen to button
transitive verb
1. : to loose the buttons of : unfasten by loosing buttons
unbuttoned his coat
also : to remove (a button) from a buttonhole
2. : to open as if by unbuttoning
unbuttoned my heart to him — Omnibook
a team of experts in the code room has unbuttoned it — E.O.Hauser
specifically : to open the hatches or apertures of (an armored vehicle)
intransitive verb
: to undo a button