unbutton

Verb

unbutton (third-person singular simple present unbuttons, present participle unbuttoning, simple past and past participle unbuttoned)

1. (ambitransitive) To open (something) by undoing its buttons.
   • Being now too high wound up to bear a delay, he unbutton'd, and drawing out the engine of love-assaults, drove it currently, as at a ready-made breach1749, [John Cleland], “(Please specify the letter or volume)”, in Memoirs of a Woman of Pleasure [Fanny Hill], London: […] [Thomas Parker] for G. Fenton [i.e., Fenton and Ralph Griffiths] […], →OCLC
   • "Mr Baxter, I think?" said the latter. He had laid aside his dripping umbrella and was unbuttoning overcoat and coat to reach an inner pocket.1914, Ernest Bramah, Max Carrados
2. (ergative, intransitive) To come open by having its buttons unfastened.
   • He was so muscled and firm, and the canvas shirt under his jacket unbuttoned easily.2010, Janet Chapman, Tempt Me If You Can, page 70