unzip
/ʌnˈzɪp/ verb [T] (present participle unzipping, past tense and past participle unzipped)
› to open something by using its zip (= two rows of metal or plastic points that fasten two sides together) : He unzipped his trousers.
› to make a file bigger again after it has been zipped (= made smaller so that you can send or store it) so that it can easily be used