• IPA: /ʌnˈbʌtən/

unbutton (unbuttons, present participle unbuttoning; past and past participle unbuttoned)

1. (ambitransitive) To open (something) by undoing its buttons.
   • 1749, [John Cleland], “(Please specify the letter or volume)”, in Memoirs of a Woman of Pleasure [Fanny Hill], London: Printed [by Thomas Parker] for G. Fenton [i.e., Fenton and Ralph Griffiths] […], OCLC 731622352 ↗:

     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 breach

2. (intransitive, ergative) To come open by having its buttons unfastened.
   • 2010, Janet Chapman, Tempt Me If You Can (page 70)

     He was so muscled and firm, and the canvas shirt under his jacket unbuttoned easily.

• German: aufknöpfen
• Italian: sbottonare
• Portuguese: desabotoar
• Spanish: desabotonar