A padded envelope is a postal cover lined to protect what is inside. Post it in a padded envelope.
The old paper ones shed grey fluff over everything, which is why bubble replaced them. A padded envelope costs less to send than a box of the same contents.
1nounpadded envelopeA postal cover lined to protect what is inside.
“The padded envelope arrived flat and the contents did not.”
padded envelope is an envelope.
Practised in Bank & Post Office