It is often used to describe the movement of water, particularly the tide going out.
Examples:
* "The tide ebbed, leaving the beach exposed."
* "His enthusiasm for the project ebbed as time went on."
Synonyms:
* Recede
* Decline
* Diminish
* Retreat
* Subside
Antonyms:
* Flow
* Rise
* Increase
* Advance
* Surge