Antonyms of verb unfasten

2 senses of unfasten

Sense 1
unfasten -- (cause to become undone; "unfasten your belt")
       Antonym of fasten (Sense 1)
      => fasten, fix, secure -- (cause to be firmly attached; "fasten the lock onto the door"; "she fixed her gaze on the man")

Sense 2
unfasten -- (become undone or untied; "The shoelaces unfastened")
       Antonym of fasten (Sense 2)
      => fasten -- (become fixed or fastened; "This dress fastens in the back")

Synonyms/Hypernyms (Ordered by Estimated Frequency) of verb unfasten

2 senses of unfasten

Sense 1
unfasten -- (cause to become undone; "unfasten your belt")
       => undo -- (cancel, annul, or reverse an action or its effect; "I wish I could undo my actions")

Sense 2
unfasten -- (become undone or untied; "The shoelaces unfastened")
       => open, open up -- (become open; "The door opened")