(=unfastened)
[shoelaces, buttons, zip, knot] défait(e)
→ Your shoelaces are undone.
→ She went to the lavatory to check if her trouser zip was undone.
→ The fact that one of his fly buttons was undone is unlikely to have fazed him
→ Her blouse was undone
to come undone
[blouse, dress, shoelaces, buttons, zip, knot] se défaire
→ His shoelaces came undone.