Verb
To loose the buttons of; to unfasten.
Source: Webster's dictionaryWhat is the life of man! Is it not to shift from side to side? From sorrow to sorrow? To button up one cause of vexation! And unbutton another! Laurence Sterne
My high school girlfriend would ask if I finally learned how to unbutton the back of a sweater! Breckin Meyer
I'm a militant fundamentalist atheist. I'm going to get on a crowded train, unbutton my coat and say rational things. People will be hurt. Ricky Gervais
unbutton the shirt Source: Internet
He’s already got one hand out to grab his jacket off the back of the chair and the other hand starting to unbutton his shirt. Source: Internet
Let’s pull”, and then the assistants unbutton the uniforms and breathe through the mouth. Source: Internet