From Longman Dictionary of Contemporary EnglishJiffy bagˈJiffy bag noun [countable] trademark British EnglishTCM a thick soft envelope, used for posting things that might break
Examples from the Corpus
Jiffy bag• He opened it carefully and extracted a padded brown Jiffy bag.• Please post loans back in a sound Jiffy bag to prevent damage.From Longman Business DictionaryJiffy bagJif‧fy bag /ˈdʒɪfi bæg/ noun [countable] trademark a thick soft envelope, used for posting things that might break 