1. not able to be delivered or transported to the intended recipient
Usage: commonly used for mail, packages, and messages

Examples

• The package was marked as undeliverable due to an incorrect address.
• Several emails were returned as undeliverable because the recipient’s mailbox was full.
• The postal service holds undeliverable mail for thirty days before disposing of it.
• Her letter came back stamped ‘undeliverable’ because the family had moved.
• The company’s automated system flags undeliverable messages for review.
• Many holiday cards were undeliverable because of the recent address changes.