unfasten (unfastens, present participle unfastening; past and past participle unfastened)

1. (transitive) To detach from any connecting agency or link#Noun|link; to disconnect#Verb|disconnect.
   • c. 1596–1599, William Shakespeare, “The Second Part of Henry the Fourth, […]”, in Mr. William Shakespeares Comedies, Histories, & Tragedies: Published According to the True Originall Copies (First Folio), London: Printed by Isaac Iaggard, and Ed[ward] Blount, published 1623, OCLC 606515358 ↗, [Act IV, scene i]:

     He doth unfasten so and shake a friend.

2. (intransitive) To come unloosed#Adjective|unloosed or untied#Adjective|untied.

• undo

• do up
• button
• button up
• tie up
• zip
• zip up

• French: défaire
• German: abschnallen, lösen, losmachen
• Russian: развя́зывать
• Spanish: desabrochar

• Italian: sciogliere, svergare
• Russian: развя́зываться